Globally replace text in several files

Globally replace text in several files
You are encouraged to solve this task according to the task description, using any language you may know.

Task

Replace every occurring instance of a piece of text in a group of text files with another one.

For this task we want to replace the text   "Goodbye London!"   with   "Hello New York!"   for a list of files.

11l

<lang 11l>L(fname) fs:list_dir(‘.’)

  I fname.ends_with(‘.txt’)
     V fcontents = File(fname).read()
     File(fname, ‘w’).write(fcontents.replace(‘Goodbye London!’, ‘Hello, New York!’))

</lang>

Ada

<lang Ada>with Ada.Strings.Unbounded, Ada.Text_IO, Ada.Command_Line, Ada.Directories;

procedure Global_Replace is

  subtype U_String is Ada.Strings.Unbounded.Unbounded_String;
  function "+"(S: String) return U_String renames
    Ada.Strings.Unbounded.To_Unbounded_String;
  function "-"(U: U_String) return String renames
    Ada.Strings.Unbounded.To_String;

  procedure String_Replace(S: in out U_String; Pattern, Replacement: String) is
     -- example: if S is "Mary had a XX lamb", then String_Replace(S, "X", "little");
     --          will turn S into "Mary had a littlelittle lamb"
     --          and String_Replace(S, "Y", "small"); will not change S

     Index : Natural;
  begin
     loop
        Index := Ada.Strings.Unbounded.Index(Source => S, Pattern => Pattern);
        exit when Index = 0;
        Ada.Strings.Unbounded.Replace_Slice
          (Source => S, Low => Index, High => Index+Pattern'Length-1,
           By => Replacement);
     end loop;
  end String_Replace;

  procedure File_Replace(Filename: String; Pattern, Replacement: String) is
     -- applies String_Rplace to each line in the file with the given Filename
     -- propagates any exceptions, when, e.g., the file does not exist 

     I_File, O_File: Ada.Text_IO.File_Type;
     Line: U_String;
     Tmp_Name: String := Filename & ".tmp"; 
        -- name of temporary file; if that file already exists, it will be overwritten
  begin
     Ada.Text_IO.Open(I_File, Ada.Text_IO.In_File, Filename);
     Ada.Text_IO.Create(O_File, Ada.Text_IO.Out_File, Tmp_Name);
     while not Ada.Text_IO.End_Of_File(I_File) loop
        Line := +Ada.Text_IO.Get_Line(I_File);
        String_Replace(Line, Pattern, Replacement);
        Ada.Text_IO.Put_Line(O_File, -Line);
     end loop;
     Ada.Text_IO.Close(I_File);
     Ada.Text_IO.Close(O_File);
     Ada.Directories.Delete_File(Filename);
     Ada.Directories.Rename(Old_Name => Tmp_Name, New_Name => Filename);
  end File_Replace;

  Pattern:     String := Ada.Command_Line.Argument(1);
  Replacement: String :=  Ada.Command_Line.Argument(2);

begin

  Ada.Text_IO.Put_Line("Replacing """ & Pattern
                         & """ by """ & Replacement & """ in"
                         & Integer'Image(Ada.Command_Line.Argument_Count - 2)
                         & " files.");
  for I in 3 .. Ada.Command_Line.Argument_Count loop
     File_Replace(Ada.Command_Line.Argument(I), Pattern, Replacement);
  end loop;

end Global_Replace;</lang>

Ouput:

> ls ?.txt
1.txt  2.txt  x.txt  y.txt

> more 2.txt
This is a text.
"Goodbye London!" 
"Goodbye London!" 
"Byebye London!" "Byebye London!" "Byebye London!" 

> ./global_replace "Goodbye London" "Hello New York" ?.txt
Replacing "Goodbye London" by "Hello New York" in 4 files.

> more 2.txt
This is a text.
"Hello New York!" 
"Hello New York!" 
"Byebye London!" "Byebye London!" "Byebye London!" 

AutoHotkey

<lang AutoHotkey>SetWorkingDir %A_ScriptDir%  ; Change the working directory to the script's location listFiles := "a.txt|b.txt|c.txt" ; Define a list of files in the current working directory loop, Parse, listFiles, | { ; The above parses the list based on the | character fileread, contents, %A_LoopField% ; Read the file fileDelete, %A_LoopField%  ; Delete the file stringReplace, contents, contents, Goodbye London!, Hello New York!, All ; replace all occurrences fileAppend, %contents%, %A_LoopField% ; Re-create the file with new contents } </lang>

AWK

<lang AWK>

1. syntax: GAWK -f GLOBALLY_REPLACE_TEXT_IN_SEVERAL_FILES.AWK filename(s)

BEGIN {

   old_text = "Goodbye London!"
   new_text = "Hello New York!"

} BEGINFILE {

   nfiles_in++
   text_found = 0
   delete arr

} { if (gsub(old_text,new_text,$0) > 0) {

     text_found++
   }
   arr[FNR] = $0

} ENDFILE {

   if (text_found > 0) {
     nfiles_out++
     close(FILENAME)
     for (i=1; i<=FNR; i++) {
       printf("%s\n",arr[i]) >FILENAME
     }
   }

} END {

   printf("files: %d read, %d updated\n",nfiles_in,nfiles_out)
   exit(0)

} </lang>

Works with: gawk

<lang awk>@include "readfile" BEGIN {

   while(++i < ARGC) 
       print gensub("Goodbye London!","Hello New York!","g", readfile(ARGV[i])) > ARGV[i] 

}</lang>

BASIC

Works with: FreeBASIC

Pass the files on the command line (i.e. global-replace *.txt).

<lang qbasic>CONST matchtext = "Goodbye London!" CONST repltext = "Hello New York!" CONST matchlen = LEN(matchtext)

DIM L0 AS INTEGER, x AS INTEGER, filespec AS STRING, linein AS STRING

L0 = 1 WHILE LEN(COMMAND$(L0))

   filespec = DIR$(COMMAND$(L0))
   WHILE LEN(filespec)
       OPEN filespec FOR BINARY AS 1
           linein = SPACE$(LOF(1))
           GET #1, 1, linein
           DO
               x = INSTR(linein, matchtext)
               IF x THEN
                   linein = LEFT$(linein, x - 1) & repltext & MID$(linein, x + matchlen)
                   ' If matchtext and repltext are of equal length (as in this example)
                   ' then you can replace the above line with this:
                   ' MID$(linein, x) = repltext
                   ' This is somewhat more efficient than having to rebuild the string.
               ELSE
                   EXIT DO
               END IF
           LOOP
       ' If matchtext and repltext are of equal length (as in this example), or repltext
       ' is longer than matchtext, you could just write back to the file while it's open
       ' in BINARY mode, like so:
       ' PUT #1, 1, linein
       ' But since there's no way to reduce the file size via BINARY and PUT, we do this:
       CLOSE
       OPEN filespec FOR OUTPUT AS 1
           PRINT #1, linein;
       CLOSE
       filespec = DIR$
   WEND
   L0 += 1

WEND</lang>

BBC BASIC

Works with: BBC BASIC for Windows

<lang bbcbasic> FindThis$ = "Goodbye London!"

     ReplaceWith$ = "Hello New York!"
     
     DIM Files$(3)
     Files$() = "C:\test1.txt", "C:\test2.txt", "C:\test3.txt", "C:\test4.txt"
     
     FOR f% = 0 TO DIM(Files$(),1)
       infile$ = Files$(f%)
       infile% = OPENIN(infile$)
       IF infile%=0 ERROR 100, "Failed to open file " + infile$
       tmpfile$ = @tmp$+"replace.txt"
       tmpfile% = OPENOUT(tmpfile$)
       
       WHILE NOT EOF#infile%
         INPUT #infile%, a$
         IF ASCa$=10 a$ = MID$(a$,2)
         l% = LEN(FindThis$)
         REPEAT
           here% = INSTR(a$, FindThis$)
           IF here% a$ = LEFT$(a$,here%-1) + ReplaceWith$ + MID$(a$,here%+l%)
         UNTIL here% = 0
         PRINT #tmpfile%, a$ : BPUT #tmpfile%,10
       ENDWHILE
       CLOSE #infile%
       CLOSE #tmpfile%
       
       OSCLI "DEL """ + infile$ + """"
       OSCLI "REN """ + tmpfile$ + """ """ + infile$ + """"
     NEXT
     END</lang>

C

<lang C>#include <stdio.h>

1. include <stdlib.h>
2. include <stddef.h>
3. include <string.h>
4. include <sys/types.h>
5. include <fcntl.h>
6. include <sys/stat.h>
7. include <unistd.h>
8. include <err.h>
9. include <string.h>

char * find_match(const char *buf, const char * buf_end, const char *pat, size_t len) { ptrdiff_t i; char *start = buf; while (start + len < buf_end) { for (i = 0; i < len; i++) if (start[i] != pat[i]) break;

if (i == len) return (char *)start; start++; } return 0; }

int replace(const char *from, const char *to, const char *fname) {

1. define bail(msg) { warn(msg" '%s'", fname); goto done; }

struct stat st; int ret = 0; char *buf = 0, *start, *end; size_t len = strlen(from), nlen = strlen(to); int fd = open(fname, O_RDWR);

if (fd == -1) bail("Can't open"); if (fstat(fd, &st) == -1) bail("Can't stat"); if (!(buf = malloc(st.st_size))) bail("Can't alloc"); if (read(fd, buf, st.st_size) != st.st_size) bail("Bad read");

start = buf; end = find_match(start, buf + st.st_size, from, len); if (!end) goto done; /* no match found, don't change file */

ftruncate(fd, 0); lseek(fd, 0, 0); do { write(fd, start, end - start); /* write content before match */ write(fd, to, nlen); /* write replacement of match */ start = end + len; /* skip to end of match */ /* find match again */ end = find_match(start, buf + st.st_size, from, len); } while (end);

/* write leftover after last match */ if (start < buf + st.st_size) write(fd, start, buf + st.st_size - start);

done: if (fd != -1) close(fd); if (buf) free(buf); return ret; }

int main() { const char *from = "Goodbye, London!"; const char *to = "Hello, New York!"; const char * files[] = { "test1.txt", "test2.txt", "test3.txt" }; int i;

for (i = 0; i < sizeof(files)/sizeof(char*); i++) replace(from, to, files[i]);

return 0; }</lang>

C#

<lang csharp> using System.Collections.Generic; using System.IO;

class Program {

   static void Main() {
       var files = new List<string> {
           "test1.txt",
           "test2.txt"
       };
       foreach (string file in files) {
           File.WriteAllText(file, File.ReadAllText(file).Replace("Goodbye London!", "Hello New York!"));
       }
   }

} </lang>

C++

<lang cpp>#include <fstream>

1. include <iterator>
2. include <boost/regex.hpp>
3. include <string>
4. include <iostream>

int main( int argc , char *argv[ ] ) {

  boost::regex to_be_replaced( "Goodbye London\\s*!" ) ;
  std::string replacement( "Hello New York!" ) ;
  for ( int i = 1 ; i < argc ; i++ ) {
     std::ifstream infile ( argv[ i ] ) ;
     if ( infile ) {

std::string filetext( (std::istreambuf_iterator<char>( infile )) , std::istreambuf_iterator<char>( ) ) ; std::string changed ( boost::regex_replace( filetext , to_be_replaced , replacement )) ; infile.close( ) ; std::ofstream outfile( argv[ i ] , std::ios_base::out | std::ios_base::trunc ) ; if ( outfile.is_open( ) ) { outfile << changed ; outfile.close( ) ; }

     }
     else 

std::cout << "Can't find file " << argv[ i ] << " !\n" ;

  }
  return 0 ;

}</lang>

Modern C++ version: <lang cpp>#include <regex>

1. include <fstream>

using namespace std; using ist = istreambuf_iterator<char>; using ost = ostreambuf_iterator<char>;

int main(){

   auto from = "Goodbye London!", to = "Hello New York!";
   for(auto filename : {"a.txt", "b.txt", "c.txt"}) {
       ifstream infile {filename};
       string content {ist {infile}, ist{}};
       infile.close();
       ofstream outfile {filename};
       regex_replace(ost {outfile}, begin(content), end(content), regex {from}, to);
   }
   return 0;

} </lang>

Clojure

<lang clojure>(defn hello-goodbye [& more]

 (doseq [file more]
   (spit file (.replace (slurp file) "Goodbye London!" "Hello New York!"))))</lang>

Common Lisp

<lang Lisp> (defun hello-goodbye (files)

 (labels ((replace-from-file (file)
            (with-open-file (in file)
              (loop for line = (read-line in nil)
                 while line do
                   (loop for index = (search "Goodbye London!" line)
                      while index do
                        (setf (subseq line index) "Hello New York!"))
                 collecting line)))
          (write-lines-to-file (lines file)
            (with-open-file (out file :direction :output :if-exists :overwrite)
              (dolist (line lines)
                (write-line line out))))
          (replace-in-file (file)
            (write-lines-to-file (replace-from-file file) file)))
   (map nil #'replace-in-file files)))

</lang>

D

Works with: D version 2

<lang d>import std.file, std.array;

void main() {

   auto from = "Goodbye London!", to = "Hello, New York!";
   foreach (fn; "a.txt b.txt c.txt".split()) {
       write(fn, replace(cast(string)read(fn), from, to));
   }

}</lang>

Delphi

Library: System.SysUtils

Library: System.IoUtils

<lang Delphi> program Globally_replace_text_in_several_files;

{$APPTYPE CONSOLE}

uses

 System.SysUtils,
 System.IoUtils;

procedure StringReplaceByFile(_old, _new: string; FileName: TFilename;

 ReplaceFlags: TReplaceFlags = []); overload

var

 Text: string;

begin

 if not FileExists(FileName) then
   exit;
 Text := TFile.ReadAllText(FileName);
 TFile.Delete(FileName);
 TFile.WriteAllText(StringReplace(Text, _old, _new, ReplaceFlags), FileName);

end;

procedure StringReplaceByFile(_old, _new: string; FileNames: TArray<TFileName>;

 ReplaceFlags: TReplaceFlags = []); overload;

begin

 for var fn in FileNames do
   StringReplaceByFile(_old, _new, fn);

end;

begin

 StringReplaceByFile('Goodbye London!', 'Hello New York!', ['a.txt', 'b.txt', 'c.txt']);

end.</lang>

Erlang

<lang Erlang> -module( globally_replace_text ).

-export( [in_files/3, main/1] ).

in_files( Old, New, Files ) when is_list(Old) ->

       in_files( binary:list_to_bin(Old), binary:list_to_bin(New), Files );

in_files( Old, New, Files ) -> [replace_in_file(Old, New, X, file:read_file(X)) || X <- Files].

main( [Old, New | Files] ) -> in_files( Old, New, Files ).

replace_in_file( Old, New, File, {ok, Binary} ) -> replace_in_file_return( File, file:write_file(File, binary:replace(Binary, Old, New, [global])) ); replace_in_file( _Old, _New, File, {error, Error} ) ->

       io:fwrite( "Error: Could not read ~p: ~p~n", [File, Error] ),
       error.

replace_in_file_return( _File, ok ) -> ok; replace_in_file_return( File, {error, Error} ) -> io:fwrite( "Error: Could not write ~p: ~p~n", [File, Error] ),

       error.

</lang>

Output:

macbook-pro:rosettacode bengt$ ls ?.txt
1.txt	2.txt
macbook-pro:rosettacode bengt$ more ?.txt
"Goodbye London!" 
"Goodbye London!" 
"Byebye London!" "Byebye London!" "Byebye London!"
...skipping...
"Goodbye London!" 
"Byebye London!" "Byebye London!" "Byebye London!"
"Goodbye London!"
macbook-pro:rosettacode bengt$ escript globally_replace_text.erl "Goodbye London\!" "Hello New York\!" ?.txt
macbook-pro:rosettacode bengt$ more ?.txt
"Hello New York!" 
"Hello New York!" 
"Byebye London!" "Byebye London!" "Byebye London!"
...skipping...
"Hello New York!" 
"Byebye London!" "Byebye London!" "Byebye London!"
"Hello New York!"

F#

<lang fsharp>open System.IO

[<EntryPoint>] let main args =

   let textFrom = "Goodbye London!"
   let textTo = "Hello New York!"
   for name in args do
       let content = File.ReadAllText(name)
       let newContent = content.Replace(textFrom, textTo)
       if content <> newContent then
           File.WriteAllText(name, newContent)
   0</lang>

Factor

Works with: Factor version 0.99 2019-10-06

<lang factor>USING: fry io.encodings.utf8 io.files kernel qw sequences splitting ;

global-replace ( files old new -- )

   '[
       [ utf8 file-contents _ _ replace ]
       [ utf8 set-file-contents ] bi
   ] each ;

qw{ a.txt b.txt c.txt } "Goodbye London!" "Hello New York!" global-replace</lang>

Fortran

This is in the style of F77 and solves the usual problem of "how long is a piece of string" by choosing a size that is surely long enough. Thus, CHARACTER*6666 ALINE. Fortran 2003 allows the alteration of the length of a character variable, but, unless there is a facility whereby in something like READ(F,11) ALINE the size of ALINE is adjusted to suit the record being read, this doesn't help much. The Q format code allows discovery of the length of a record as it is being read, and so only the required portion, ALINE(1:L), of an input record is placed and trailing spaces out to 6666 are not supplied nor need they be scanned. Thus an input record that has trailing spaces will have them preserved - unless the text replacement changes spaces...

The search is done by using the supplied INDEX function which alas rarely has an option to specify the starting point via an additional (optional?) parameter. So this must be done via INDEX(ALINE(L1:L),THIS) and then one must carefully consider offsets and the like while counting on fingers and becoming confused. On the other hand, it handles annoyances such as ALINE(L1:L) being shorter than THIS. The expression ALINE(L1:L) does not create a new string variable by copying the specified text, it works (or should work!) via offsets into ALINE. Similarly, there is no attempt to concatenate an output string to write in one go as that too would involve copying text about. Though WRITE statements involve no small overhead in themselves. Although if LEN(THIS) = LEN(THAT) as is the case in the example task an alter-in-place could be used and ALINE(1:L) be written out in one go, the more general approach is used of writing text up to the start of a match, writing out the replacement THAT, and scanning beyond the match for the next text until the tail end.

The file to be altered cannot be changed "in-place", as by writing back an altered record even if the text replacement does not involve a change in length because such a facility is not available for text files that are read and written sequentially only. More accomplished file systems may well offer varying-length records with update possible even of longer or shorter new versions but standard Fortran does not demand such facilities. So, the altered content has to be written to a temporary file (or perhaps could be held in a capacious memory) which is then read back to overwrite the original file. It would be safer to rename the original file and write to a new version, but Fortran typically does not have access to any file renaming facilities and the task calls for an overwrite anyway. So, overwrite it is, which is actually a file delete followed by a write.

Once equipped with a subroutine that applies a specified change to a named disc file, there is no difficulty in invoking it for a horde of disc files. A more civilised routine might make reports about the files assaulted and the number of changes, and also be prepared to report various oddities such as a file being available but not for WRITE. It is for this reason that the source file is opened with READWRITE even though it at that stage is only going to be read from.<lang Fortran> SUBROUTINE FILEHACK(FNAME,THIS,THAT) !Attacks a file!

      CHARACTER*(*) FNAME	!The name of the file, presumed to contain text.
      CHARACTER*(*) THIS	!The text sought in each record.
      CHARACTER*(*) THAT	!Its replacement, should it be found.
      INTEGER F,T		!Mnemonics for file unit numbers.
      PARAMETER (F=66,T=67)	!These should do.
      INTEGER L		!A length
      CHARACTER*6666 ALINE	!Surely sufficient?
      LOGICAL AHIT		!Could count them, but no report is called for.
       INQUIRE(FILE = FNAME, EXIST = AHIT)	!This mishap is frequent, so attend to it.
       IF (.NOT.AHIT) RETURN			!Nothing can be done!
       OPEN (F,FILE=FNAME,STATUS="OLD",ACTION="READWRITE")	!Grab the source file.
       OPEN (T,STATUS="SCRATCH")	!Request a temporary file.
       AHIT = .FALSE.		!None found so far.

Chew through the input, replacing THIS by THAT while writing to the temporary file..

  10   READ (F,11,END = 20) L,ALINE(1:MIN(L,LEN(ALINE)))	!Grab a record.
       IF (L.GT.LEN(ALINE)) STOP "Monster record!"		!Perhaps unmanageable.
  11   FORMAT (Q,A)		!Obviously, Q = length of characters unread in the record.
       L1 = 1			!Start at the start.
  12   L2 = INDEX(ALINE(L1:L),THIS)	!Look from L1 onwards.
       IF (L2.LE.0) THEN		!A hit?
         WRITE (T,13) ALINE(L1:L)	!No. Finish with the remainder of the line.
  13     FORMAT (A)			!Thus finishing the output line.
         GO TO 10			!And try for the next record.
       END IF				!So much for not finding THIS.
  14   L2 = L1 + L2 - 2	!Otherwise, THIS is found, starting at L1.
       WRITE (T,15) ALINE(L1:L2)	!So roll the text up to the match, possibly none.
  15   FORMAT (A,$)			!But not ending the record.
       WRITE (T,15) THAT		!Because THIS is replaced by THAT.
       AHIT = .TRUE.			!And we've found at least one match.
       L1 = L2 + LEN(THIS) + 1		!Finger the first character beyond the matching THIS.
       IF (L - L1 + 1 .GE. LEN(THIS)) GO TO 12	!Might another search succeed?
       WRITE (T,13) ALINE(L1:L)	!Nope. Finish the line with the tail end.
       GO TO 10		!And try for another record.

Copy the temporary file back over the source file. Hope for no mishap and data loss!

  20   IF (AHIT) THEN	!If there were no hits, there is nothing to do.
         CLOSE (F)		!Oh well.
         REWIND T		!Go back to the start.
         OPEN (F,FILE="new"//FNAME,STATUS = "REPLACE",ACTION = "WRITE")	!Overwrite...
  21     READ (T,11,END = 22) L,ALINE(1:MIN(L,LEN(ALINE)))	!Grab a line.
         IF (L.GT.LEN(ALINE)) STOP "Monster changed record!"	!Once you start checking...
         WRITE (F,13) ALINE(1:L) 		!In case LEN(THAT) > LEN(THIS)
         GO TO 21			!Go grab the next line.
       END IF		!So much for the replacement of the file.
  22   CLOSE(T)	!Finished: it will vanish.
       CLOSE(F)	!Hopefully, the buffers will be written.
     END	!So much for that.

     PROGRAM ATTACK
     INTEGER N
     PARAMETER (N = 6)		!More than one, anyway.
     CHARACTER*48 VICTIM(N)	!Alternatively, the file names could be read from a file
     DATA VICTIM/		!Along with the target and replacement texts in each case.
    1 "StaffStory.txt",
    2 "Accounts.dat",
    3 "TravelAgent.txt",
    4 "RemovalFirm.dat",
    5 "Addresses.txt",
    6 "SongLyrics.txt"/	!Invention flags.

     DO I = 1,N	!So, step through the list.
       CALL FILEHACK(VICTIM(I),"Goodbye London!","Hello New York!")	!One by one.
     END DO		!On to the next.

     END</lang>

Go

<lang go>package main

import (

   "bytes"
   "io/ioutil"
   "log"
   "os"

)

func main() {

   gRepNFiles("Goodbye London!", "Hello New York!", []string{
       "a.txt",
       "b.txt",
       "c.txt",
   })

}

func gRepNFiles(olds, news string, files []string) {

   oldb := []byte(olds)
   newb := []byte(news)
   for _, fn := range files {
       if err := gRepFile(oldb, newb, fn); err != nil {
           log.Println(err)
       }
   }

}

func gRepFile(oldb, newb []byte, fn string) (err error) {

   var f *os.File
   if f, err = os.OpenFile(fn, os.O_RDWR, 0); err != nil {
       return
   }
   defer func() {
       if cErr := f.Close(); err == nil {
           err = cErr
       }
   }()
   var b []byte
   if b, err = ioutil.ReadAll(f); err != nil {
       return
   }
   if bytes.Index(b, oldb) < 0 {
       return
   }
   r := bytes.Replace(b, oldb, newb, -1)
   if err = f.Truncate(0); err != nil {
       return
   }
   _, err = f.WriteAt(r, 0)
   return

}</lang>

Haskell

The module Data.List provides some useful functions: tails (constructs substrings dropping elements from the head of the list), isPrefixOf (checks if a string matches the beginning of another one) and elemIndices (gets the list indices of all elements matching a value). This code doesn't rewrite the files, it just returns the changes made to the contents of the files. <lang Haskell>import Data.List (tails, elemIndices, isPrefixOf)

replace :: String -> String -> String -> String replace [] _ xs = xs replace _ [] xs = xs replace _ _ [] = [] replace a b xs = replAll

   where
       -- make substrings, dropping one element each time
       xtails = tails xs
       -- what substrings begin with the string to replace?
       -- get their indices
       matches = elemIndices True $ map (isPrefixOf a) xtails
       -- replace one occurrence
       repl ys n = take n ys ++ b ++ drop (n + length b) ys
       -- replace all occurrences consecutively
       replAll = foldl repl xs matches

replaceInFiles a1 a2 files = do

   f <- mapM readFile files
   return $ map (replace a1 a2) f

</lang> This other version is more effective because it processes the string more lazily, replacing the text as it consumes the input string (the previous version was stricter because of "matches" traversing the whole list; that would force the whole string into memory, which could cause the system to run out of memory with large text files). <lang Haskell>replace :: Eq a => [a] -> [a] -> [a] -> [a] replace a b = go

 where
   w = length a
   go [] = []
   go xxs@(x : xs)
     | a `isPrefixOf` xxs = b <> go (drop w xxs)
     | otherwise = x : go xs</lang>

and with different library imports, we could also write things like: <lang haskell>import Data.List (intercalate) import Data.List.Split (splitOn)

replace :: String -> String -> String -> String replace a b = intercalate b . splitOn a</lang>

Example:

File "t1.txt" contains: "Goodbye London! This is text 1."
File "t2.txt" contains: "This is text 2. Goodbye London! Now we repeat: Goodbye London! And that's all."

replaceInFiles "Goodbye London!" "Hello New York!" ["t1.txt", "t2.txt"]

Output:

["Hello New York! This is text 1.\n","This is text 2. Hello New York! Now we repeat: Hello New York! And that's all.\n"]

Icon and Unicon

This example uses the Unicon stat function. It can be rewritten for Icon to aggregate the file in a reads loop. <lang Icon>procedure main() globalrepl("Goodbye London","Hello New York","a.txt","b.txt") # variable args for files end

procedure globalrepl(old,new,files[])

every fn := !files do

  if s := reads(f := open(fn,"bu"),stat(f).size) then {
     writes(seek(f,1),replace(s,old,new))
     close(f)
     }
  else write(&errout,"Unable to open ",fn)

end

link strings # for replace</lang>

Library: Icon Programming Library

strings.icn provides replace.

J

If files is a variable with the desired list of file names:

<lang j>require'strings' (1!:2~rplc&('Goodbye London!';'Hello New York!')@(1!:1))"0 files</lang>

Java

Minimalistic version, assumes default encoding.

Works with: Java version 7

<lang java>import java.io.*; import java.nio.file.*;

public class GloballyReplaceText {

   public static void main(String[] args) throws IOException {

       for (String fn : new String[]{"test1.txt", "test2.txt"}) {
           String s = new String(Files.readAllBytes(Paths.get(fn)));
           s = s.replace("Goodbye London!", "Hello New York!");
           try (FileWriter fw = new FileWriter(fn)) {
               fw.write(s);
           }
       }
   }

}</lang>

In Java 11 the body could be shortened to: <lang java> for (String fn : List.of("file1.txt","file2.txt")) { Path path = Path.of(fn); Files.writeString(path, Files.readString(path).replace("Goodbye London!", "Hello New York!")); } </lang>

jq

Works with: jq version 1.5

jq delegates filename manipulation to the shell. For simplicity, in the following we assume the availability of `sponge` to simplify the mechanics of editing a file "in-place". <lang bash>for file do

 jq -Rr 'gsub($from; $to)' --arg from 'Goodbye London!' --arg to 'Hello New York!' "$file" | 
   sponge "$file"

done</lang>

The jq filter used above is `gsub/2`, which however is designed for regular expressions. Here is a string-oriented alternative: <lang jq>def gsubst($from; $to):

 ($from | length) as $len
 | def g:
     index($from) as $ix
     | if $ix then .[:$ix]  + $to +  (.[($ix+$len):] | g) else . end;
    g;</lang>

Jsish

For the demo, the code does not overwrite the samples, but creates a .new file. <lang javascript>/* Global replace in Jsish */ if (console.args.length == 0) {

   console.args.push('-');

}

/* For each file, globally replace "Goodbye London!" with "Hello New York!" */ var fn, data, changed; for (fn of console.args) {

   /* No args, or an argument of - uses "stdin" (a special Channel name) */
   if (fn == 'stdin') fn = './stdin';
   if (fn == '-') fn = 'stdin';
   try {
       data = File.read(fn);
       /* Jsi supports the m multiline regexp flag */
       changed = data.replace(/Goodbye London!/gm, 'Hello New York!');
       if (changed != data) {
           if (fn == 'stdin') fn = 'stdout'; else fn += '.new';
           var cnt = File.write(fn, changed);
           puts(fn + ":" + cnt, 'updated');
       }
   } catch(err) { puts(err, 'processing', fn); }

}</lang>

To meet the task specification, change

<lang javascript>if (fn == 'stdin') fn = 'stdout'; else fn += '.new';</lang>

to

<lang javascript>if (fn == 'stdin') fn = 'stdout';</lang>

removing the else clause. The code will then overwrite originals.

Output:

prompt$ cat one
Goodbye London! it was the slice.
Goodbye London, should still be here
And a little more Goodbye London! New York!

prompt$ jsish global-replace.jsi - <one
Hello New York! it was the slice.
Goodbye London, should still be here
And a little more Hello New York! New York!
stdout:115 updated

Julia

We will use Julia's built-in Perl-compatible regular-expressions. Although we could read in the files line by line, it is simpler and probably faster to just read the whole file into memory (as text files are likely to fit into memory on modern computers). <lang julia>filenames = ["f1.txt", "f2.txt"] for filename in filenames

  txt = read(filename, String)
  open(filename, "w") do f
     write(f, replace(txt, "Goodbye London!" => "Hello New York!"))
  end

end</lang>

Kotlin

<lang scala>// version 1.2.0

import java.io.File

fun main(args: Array<String>) {

   val files = arrayOf("file1.txt", "file2.txt")
   for (file in files) {
       val f = File(file)
       var text = f.readText()
       println(text)
       text = text.replace("Goodbye London!", "Hello New York!")
       f.writeText(text)
       println(f.readText())
   }

}</lang>

Output:

File1 contains "Goodbye London!"

File1 contains "Hello New York!"

File2 contains "Goodbye London!"

File2 contains "Hello New York!"

Lasso

<lang Lasso>#!/usr/bin/lasso9

local(files = array('f1.txt', 'f2.txt'))

with filename in #files let file = file(#filename) let content = #file -> readbytes do { #file -> dowithclose => { #content -> replace('Goodbye London!', 'Hello New York!') #file -> opentruncate #file -> writebytes(#content) } }</lang>

Liberty BASIC

<lang lb> nomainwin

file$( 1) ="data1.txt" file$( 2) ="data2.txt" file$( 3) ="data3.txt"

for i =1 to 3

   open file$( i) for input as #i
       orig$ =input$( #i, lof( #i))
   close #i

   dummy$ =FindReplace$( orig$, "Goodbye London!", "Hello New York!", 1)

   open "RC" +file$( i) for output as #o
       #o dummy$;
   close #o

next i

end

function FindReplace$( FindReplace$, find$, replace$, replaceAll) ' Target string, string to find, string to replace it with, flag 0/1 for 'replace all occurrences'.

   if ( ( FindReplace$ <>"") and ( find$ <>"") ) then
       fLen =len( find$)
       rLen =len( replace$)
       do
           fPos =instr( FindReplace$, find$, fPos)
           if not( fPos) then exit function
           pre$            =left$( FindReplace$, fPos -1)
           post$           =mid$( FindReplace$, fPos +fLen)
           FindReplace$    =pre$ +replace$ +post$
           fPos            =fPos +( rLen -fLen) +1
       loop while (replaceAll)
   end if

end function </lang>

Lua

<lang lua>filenames = { "f1.txt", "f2.txt" }

for _, fn in pairs( filenames ) do

   fp = io.open( fn, "r" )
   str = fp:read( "*all" )
   str = string.gsub( str, "Goodbye London!", "Hello New York!" )
   fp:close()

   fp = io.open( fn, "w+" )
   fp:write( str )
   fp:close()

end</lang>

Mathematica / Wolfram Language

<lang Mathematica>listOfFiles = {"a.txt", "b.txt", "c.txt"}; Do[

filename = listOfFilesi;
filetext = Import[filename, "Text"];
filetext = StringReplace[filetext, "Goodbye London!" -> "Hello New York!"];
Export[filename, filetext, "Text"]
, {i, 1, Length[listOfFiles]}]</lang>

File b.txt before the code is run:

second file for the Globally replace text in several files problem. 
Goodbye London! 
Goodbye London!
Bye bye London! 
Bye bye London! Bye bye London!

File b.txt after the code is run:

second file for the Globally replace text in several files problem. 
Hello New York! 
Hello New York!
Bye bye London! 
Bye bye London! Bye bye London!

newLISP

Works with: newLisp version 10.7.5

<lang newLISP> (define (replace-in-file filename this bythat)

  (set 'content (read-file filename))
  (when (string? content)
    (replace this content bythat)
    (write-file filename content)
  )

)

(set 'files '("a.txt" "b.txt" "c.txt" "missing")) (dolist (fname files)

  (replace-in-file fname "Goodbye London!" "Hello New York!")

)

(exit) </lang>

Nim

<lang nim>import strutils

let fr = "Goodbye London!" let to = "Hello, New York!"

for fn in ["a.txt", "b.txt", "c.txt"]:

 fn.writeFile fn.readFile.replace(fr, to)</lang>

Objeck

<lang objeck>class ReplaceAll {

 function : Main(args : String[]) ~ Nil {
   files := ["text1.txt", "text2.txt"];
   each(f : files) {
     input := System.IO.File.FileReader->ReadFile(files[f]);
     output := input->ReplaceAll("Goodbye London!", "Hello New York!");
     System.IO.File.FileWriter->WriteFile(files[f], output)->PrintLine();
   };
 }

}</lang>

OpenEdge/Progress

<lang progress>FUNCTION replaceText RETURNS LOGICAL (

  i_cfile_list   AS CHAR,
  i_cfrom        AS CHAR,
  i_cto          AS CHAR

):

  DEF VAR ii     AS INT.
  DEF VAR lcfile AS LONGCHAR.

  DO ii = 1 TO NUM-ENTRIES( i_cfile_list ):
     COPY-LOB FROM FILE ENTRY( ii, i_cfile_list ) TO lcfile.
     lcfile = REPLACE( lcfile, i_cfrom, i_cto ).
     COPY-LOB FROM lcfile TO FILE ENTRY( ii, i_cfile_list ).
  END.
  

END FUNCTION. /* replaceText */

replaceText(

  "a.txt,b.txt,c.txt",
  "Goodbye London!",
  "Hello New York!"

).</lang>

Pascal

Works with: Free_Pascal

<lang pascal>Program StringReplace;

uses

 Classes, StrUtils;

const

 fileName: array[1..3] of string = ('a.txt', 'b.txt', 'c.txt');
 matchText = 'Goodbye London!';
 replaceText = 'Hello New York!';

var

 AllText: TStringlist;
 i, j: integer;

begin

 for j := low(fileName) to high(fileName) do
 begin
  AllText := TStringlist.Create;
  AllText.LoadFromFile(fileName[j]);
  for i := 0 to AllText.Count-1 do
    AllText.Strings[i] := AnsiReplaceStr(AllText.Strings[i], matchText, replaceText);
  AllText.SaveToFile(fileName[j]);
  AllText.Destroy;
 end;

end.</lang>

Perl

<lang bash>perl -pi -e "s/Goodbye London\!/Hello New York\!/g;" a.txt b.txt c.txt</lang>

Phix

ctrace.out was just a file that happened to be handy, obviously you'd have to provide your own file list.
as hinted, you could probably improve on the error handling.
get_text is deliberately limited to 1GB, for larger files use a temporary file, a loop of gets/puts, and delete_file/rename_file at the end.

without js -- file i/o
procedure global_replace(string s, string r, sequence file_list)
    for i=1 to length(file_list) do
        string filename = file_list[i]
        integer fn = open(filename,"rb")
        if fn=-1 then ?9/0 end if   -- message/retry?
        string text = get_text(fn)
        close(fn)
        text = substitute(text,s,r)
        fn = open(filename,"wb")
        puts(fn,text)
        close(fn)
    end for
end procedure
 
sequence file_list = {"ctrace.out"}
global_replace("Goodbye London!", "Hello New York!", file_list)

PicoLisp

<lang PicoLisp>(for File '(a.txt b.txt c.txt)

  (call 'mv File (tmp File))
  (out File
     (in (tmp File)
        (while (echo "Goodbye London!")
           (prin "Hello New York!") ) ) ) )</lang>

PowerBASIC

Translation of: BASIC

<lang powerbasic>$matchtext = "Goodbye London!" $repltext = "Hello New York!"

FUNCTION PBMAIN () AS LONG

   DIM L0 AS INTEGER, filespec AS STRING, linein AS STRING

   L0 = 1
   WHILE LEN(COMMAND$(L0))
       filespec = DIR$(COMMAND$(L0))
       WHILE LEN(filespec)
           OPEN filespec FOR BINARY AS 1
               linein = SPACE$(LOF(1))
               GET #1, 1, linein
               ' No need to jump through FB's hoops here...
               REPLACE $matchtext WITH $repltext IN linein
               PUT #1, 1, linein
               SETEOF #1
           CLOSE
           filespec = DIR$
       WEND
       INCR L0
   WEND

END FUNCTION</lang>

PowerShell

<lang PowerShell> $listfiles = @('file1.txt','file2.txt') $old = 'Goodbye London!' $new = 'Hello New York!' foreach($file in $listfiles) {

   (Get-Content $file).Replace($old,$new) | Set-Content $file

} </lang>

PureBasic

<lang PureBasic>Procedure GRTISF(List File$(), Find$, Replace$)

 Protected Line$, Out$, OutFile$, i
 ForEach File$()
   fsize=FileSize(File$())
   If fsize<=0: Continue: EndIf
   If ReadFile(0, File$())
     i=0
     ;
     ; generate a temporary file in a safe way
     Repeat
       file$=GetTemporaryDirectory()+base$+"_"+Str(i)+".tmp"
       i+1
     Until FileSize(file$)=-1
     i=CreateFile(FileID, file$)
     If i
       ; Copy the infile to the outfile while replacing any needed text
       While Not Eof(0)
         Line$=ReadString(0)
         Out$=ReplaceString(Line$,Find$,Replace$)
         WriteString(1,Out$)
       Wend
       CloseFile(1)
     EndIf
     CloseFile(0)
     If i
       ; If we made a new file, copy it back.
       CopyFile(file$, File$())
       DeleteFile(file$)
     EndIf
   EndIf
 Next

EndProcedure</lang> Implementation

NewList Xyz$()
AddElement(Xyz$()): Xyz$()="C:\\a.txt"
AddElement(Xyz$()): Xyz$()="C:\\b.txt"
AddElement(Xyz$()): Xyz$()="D:\\c.txt"

GRTISF(Xyz$(), "Goodbye London", "Hello New York")

Python

From Python docs. (Note: in-place editing does not work for MS-DOS 8+3 filesystems.).

<lang python>import fileinput

for line in fileinput.input(inplace=True):

   print(line.replace('Goodbye London!', 'Hello New York!'), end=)

</lang>

Racket

Code wrapped in a convenient script: <lang racket>

1. !/usr/bin/env racket
2. lang racket

(define from-string #f) (define to-string #f)

(command-line

#:once-each
[("-f") from "Text to remove" (set! from-string from)]
[("-t") to "Text to put instead" (set! to-string to)]
#:args files
(unless from-string (error "No `from' string specified"))
(unless to-string   (error "No `to' string specified"))
(when (null? files) (error "No files given"))
(define from-rx (regexp (regexp-quote from-string)))
(for ([file files])
  (printf "Editing ~a..." file) (flush-output)
  (define text1 (file->string file))
  (define text2 (regexp-replace* from-rx text1 to-string))
  (if (equal? text1 text2)
    (printf " no change\n")
    (begin (display-to-file text2 file #:exists 'replace)
           (printf " modified copy saved in place\n")))))

</lang> Sample run:

$ ./replace -h
replace [ <option> ... ] [<files>] ...
 where <option> is one of
  -f <from> : Text to remove
  -t <to> : Text to put instead
  --help, -h : Show this help
  -- : Do not treat any remaining argument as a switch (at this level)
 Multiple single-letter switches can be combined after one `-'; for
  example: `-h-' is the same as `-h --'
$ ./replace -f "Goodbye London!" "Hello New York!" file*
Editing file1... no change
Editing file2... modified copy saved in place
Editing file3... modified copy saved in place

Raku

(formerly Perl 6)

Current Raku implementations do not yet support the -i flag for editing files in place, so we roll our own (rather unsafe) version:

<lang perl6>slurp($_).subst('Goodbye London!', 'Hello New York!', :g) ==> spurt($_)

   for <a.txt b.txt c.txt>;</lang>

Red

<lang Red>>> f: request-file >> str: read f >> replace/all str "Goodbye London!" "Hello New York!" >> write f str</lang>

REXX

version 1

This example works under "DOS" and/or "DOS" under Microsoft Windows.

File names that contain blanks should have their blanks replaced with commas. <lang rexx>/*REXX program reads the files specified and globally replaces a string. */ old= "Goodbye London!" /*the old text to be replaced. */ new= "Hello New York!" /* " new " used for replacement. */ parse arg fileList /*obtain required list of files from CL*/

1. = words(fileList) /*the number of files in the file list.*/

  do f=1  for #;     fn= translate( word(fileList, f), , ',');     say;     say
  say '──────── file is being read: '    fn    " ("f   'out of'     #     "files)."
  call linein fn,1,0                            /*position the file for input.         */
  changes= 0                                    /*the number of changes in file so far.*/
            do rec=0  while lines(fn)\==0       /*read a file   (if it exists).        */
            @.rec= linein(fn)                   /*read a record (line)  from the file. */
            if pos(old, @.rec)==0  then iterate /*Anything to change?   No, then skip. */
            changes= changes + 1                /*flag that file contents have changed.*/
            @.rec= changestr(old, @.rec, new)   /*change the @.rec record, old ──► new.*/
            end   /*rec*/

  say '──────── file has been read: '         fn", with "      rec      'records.'
  if changes==0  then do;  say '──────── file  not  changed: '   fn;   iterate;   end
  call lineout fn,,1                            /*position file for output at 1st line.*/
  say '──────── file being changed: '   fn

      do r=0  for rec;     call lineout fn, @.r /*re─write the contents of the file.   */
      end   /*r*/

  say '──────── file was   changed: '   fn    " with"   changes   'lines changed.'
  end   /*f*/                                   /*stick a fork in it,  we're all done. */</lang>

Some older REXXes don't have a   changestr   BIF,   so one is included here   ──►   CHANGESTR.REX.

output   when using the input (list of files) of:     one.txt   two.txt

──────── file is being read:  one.txt  (1 out of 2 files).
──────── file has been read:  one.txt, with  13 records.
──────── file being changed:  one.txt
──────── file was   changed:  one.txt  with 2 lines changed.


──────── file is being read:  two.txt  (2 out of 2 files).
──────── file has been read:  two.txt, with  59 records.
──────── file being changed:  two.txt
──────── file was   changed:  two.txt  with 6 lines changed.

Version 2

considering file ids that contain blanks

<lang rexx>/* REXX ***************************************************************

• Copy all files *.txt to *.rpl
• replacing all occurrences of old by new
• Execute in the directory containing the files to be processed
• 16.01.2013 Walter Pachl
• ...if file names contain blanks
  • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • /

Parse Arg a If a='?' Then Do

 Do i=2 To 5
   Say substr(sourceline(i),3)
   End
 Exit
 End

'dir *.rpl' Say 'May I erase *.rpl?' Parse Upper Pull answer If answer='Y' | answer='J' Then

 'erase *.rpl'

Else Do

 Say 'Giving up..'
 Exit
 End

old='Goodbye London!' new='Hello New York!' dir='dir.dir' 'dir *.* >' dir Do While lines(dir)>0

 Parse Value linein(dir) With 37 f
 Select
   When f= |,
        left(f,1)='.' |,
        pos(' Bytes',f)>0 Then Iterate
   When right(f,4)='.txt' Then
     Call replace
   Otherwise
     Say left(f,50) 'not eligible for replacing'
   End
 End

Exit

replace: /* REXX ***************************************************************

• Copy a file fn.txt to fn.rpl
• replacing all occurrences of old by new
  • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • /

oid=fn(f)'.rpl' cnt.=0 Do ii=1 By 1 While lines(f)>0

 l=linein(f)
 ol=repl(l,new,old)
 Call lineout oid,ol
 End

Call lineout f Call lineout oid Select

 When cnt.0changes=0 Then Do
   'erase' oid
   Say left(f,50) 'no changes'
   End
 When cnt.0changes=1 Then 
   Say left(f,50) '1 change'
 Otherwise
   Say left(f '->' oid,50) cnt.0changes 'changes'
 End

Return

fn: Procedure /* REXX ***************************************************************

• Get the file name of a file id
  • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • /

parse Arg fid Parse Var fid fn '.' ft Return fn

repl: Procedure Expose cnt. /* REXX ***************************************************************

• Replace an old string by a new one
  • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • /

 Parse Arg s,new,old
 ol=
 Do Until p=0
   p=pos(old,s)
   If p>0 Then Do
     ol=ol||left(s,p-1)||new
     s=substr(s,p+length(old))
     cnt.0changes=cnt.0changes+1
     End
   Else
     ol=ol||s
   End
 Return ol</lang>

Sample output:

 Datenträger in Laufwerk Z: ist H
 Volumeseriennummer: FE17-3A89

 Verzeichnis von Z:\glr

16.01.2013  09:55               283 input.rpl
16.01.2013  09:55               352 input2.rpl
16.01.2013  09:55               283 input file.rpl
               3 Datei(en),            918 Bytes
               0 Verzeichnis(se),  3.993.468.928 Bytes frei
May I erase *.rpl?
  ----> here I entered y
input.txt -> input.rpl                             1 change
input.nix                                          not eligible for replacing
input2.txt -> input2.rpl                           4 changes
dir.dir                                            not eligible for replacing
input file.txt -> input file.rpl                   1 change
input3.txt                                         no changes

Ring

<lang ring> filenames = ["ReadMe.txt", "ReadMe2.txt"]

for fn in filenames

   fp = fopen(fn,"r")
   str = fread(fp,getFileSize(fp))
   str = substr(str, "Greetings", "Hello")
   fclose(fp) 

   fp = fopen(fn,"w")
   fwrite(fp, str)
   fclose(fp)

next

func getFileSize fp

    C_FILESTART = 0
    C_FILEEND = 2
    fseek(fp,0,C_FILEEND)
    nFileSize = ftell(fp)
    fseek(fp,0,C_FILESTART)
    return nFileSize

</lang>

Ruby

Like Perl:

ruby -pi -e "gsub('Goodbye London!', 'Hello New York!')" a.txt b.txt c.txt

Run BASIC

<lang runbasic>file$(1) ="data1.txt" file$(2) ="data2.txt" file$(3) ="data3.txt"

for i = 1 to 3

   open file$(i) for input as #in
       fileBefore$ = input$( #in, lof( #in))
   close #in

   fileAfter$ = strRep$(fileBefore$, "Goodbye London!", "Hello New York!")
   open "new_" +  file$(i) for output as #out
       print #out,fileAfter$;
   close #out

next i end

' -------------------------------- ' string replace - rep str with ' -------------------------------- FUNCTION strRep$(str$,rep$,with$) ln = len(rep$) ln1 = ln - 1 i = 1 while i <= len(str$)

   if mid$(str$,i,ln) = rep$ then
       strRep$ = strRep$ + with$
       i = i + ln1
   else
       strRep$ = strRep$ + mid$(str$,i,1)
   end if

i = i + 1 WEND END FUNCTION</lang>

Rust

<lang rust> //! Author: Rahul Sharma //! Github: <https://github.com/creativcoder>

use std::fs::File; use std::fs::OpenOptions; use std::io::BufRead; use std::io::BufReader; use std::io::BufWriter; use std::io::Write;

fn main() {

   // opens file for writing replaced lines
   let out_fd = OpenOptions::new()
       .write(true)
       .create(true)
       .open("resources/output.txt");

   // defining a closure write_line
   let write_line = |line: &str| match out_fd {
       Ok(ref v) => {
           let mut writer = BufWriter::new(v);
           writer.write_all(line.as_bytes()).unwrap();
       }
       Err(ref e) => {
           println!("Error:{}", e);
       }
   };
   // read input file
   match File::open("resources/paragraph.txt") {
       Ok(handle) => {
           let mut reader = BufReader::new(handle);
           let mut line = String::new();
           // read the first line
           reader.read_line(&mut line).unwrap();
           // loop until line end
           while line.trim() != "" {
               let mut replaced_line = line.trim().replace("Goodbye London!", "Hello New York!");
               replaced_line += "\n";
               write_line(&replaced_line[..]);
               line.clear();
               reader.read_line(&mut line).unwrap();
           }
       }
       Err(e) => println!("Error:{}", e),
   }

} </lang>

Output:

Scala

<lang Scala>import java.io.{File, PrintWriter}

object GloballyReplaceText extends App {

 val (charsetName, fileNames) = ("UTF8", Seq("file1.txt", "file2.txt"))
 for (fileHandle <- fileNames.map(new File(_)))
   new PrintWriter(fileHandle, charsetName) {
     print(scala.io.Source.fromFile(fileHandle, charsetName).mkString
       .replace("Goodbye London!", "Hello New York!"))
     close()
   }

}</lang>

Sed

Works with: GNU Sed

<lang bash>sed -i 's/Goodbye London!/Hello New York!/g' a.txt b.txt c.txt</lang>

Seed7

<lang seed7>$ include "seed7_05.s7i";

 include "getf.s7i";

const proc: main is func

 local
   var string: fileName is "";
   var string: content is "";
 begin
   for fileName range [] ("a.txt", "b.txt", "c.txt") do
     content := getf(fileName);
     content := replace(content, "Goodbye London!", "Hello New York!");
     putf(fileName, content);
   end for;
 end func;</lang>

Sidef

<lang ruby>var names = %w(

               a.txt
               b.txt
               c.txt
             )

  names.map{ File(_) }.each { |file|

   say file.edit { |line|
       line.gsub("Goodbye London!", "Hello New York!")
   }

}</lang>

Tcl

Library: Tcllib (Package: fileutil)

<lang tcl>package require Tcl 8.5 package require fileutil

1. Parameters to the replacement

set from "Goodbye London!" set to "Hello New York!"

1. Which files to replace

set fileList [list a.txt b.txt c.txt]

1. Make a command fragment that performs the replacement on a supplied string

set replacementCmd [list string map [list $from $to]]

1. Apply the replacement to the contents of each file

foreach filename $fileList {

   fileutil::updateInPlace $filename $replacementCmd

}</lang>

TUSCRIPT

<lang tuscript> $$ MODE TUSCRIPT files="a.txt'b.txt'c.txt"

BUILD S_TABLE search = ":Goodbye London!:"

LOOP file=files

ERROR/STOP OPEN (file,WRITE,-std-)
ERROR/STOP CREATE ("scratch",FDF-o,-std-)
 ACCESS q: READ/STREAM/RECORDS/UTF8 $file s,aken+text/search+eken
 ACCESS s: WRITE/ERASE/STREAM/UTF8 "scratch" s,aken+text+eken
  LOOP
   READ/EXIT q
   IF (text.ct.search) SET text="Hello New York!"
   WRITE/ADJUST s
  ENDLOOP
 ENDACCESS/PRINT q
 ENDACCESS/PRINT s
ERROR/STOP COPY ("scratch",file)
ERROR/STOP CLOSE (file)

ENDLOOP ERROR/STOP DELETE ("scratch") </lang>

TXR

Extraction Language

<lang txr>@(next :args) @(repeat) @file @(next `@file`) @(freeform) @(coll :gap 0)@notmatch@{match /Goodbye, London!/}@(end)@*tail@/\n/ @(output `@file.tmp`) @(rep)@{notmatch}Hello, New York!@(end)@tail @(end) @(do @(rename-path `@file.tmp` file)) @(end)</lang> Run:

$ cat foo.txt
aaaGoodbye, London!aaa
Goodbye, London!
$ cat bar.txt
aaaGoodbye, London!aaa
Goodbye, London!
$ txr replace-files.txr foo.txt bar.txt
$ cat foo.txt
aaaHello, New York!aaa
Hello, New York!
$ cat bar.txt
aaaHello, New York!aaa
Hello, New York!

Run, with no directory permissions:

$ chmod a-w .
$ txr replace-files.txr foo.txt bar.txt
txr: unhandled exception of type file_error:
txr: could not open foo.txt.tmp (error 13/Permission denied)

TXR Lisp

<lang txrlisp>(each ((fname *args*))

 (let* ((infile (open-file fname))
        (outfile (open-file `@fname.tmp` "w"))
        (content (get-string infile))
        (edited (regsub #/Goodbye, London/ "Hello, New York" content)))
   (put-string edited outfile)
   (rename-path `@fname.tmp` fname)))</lang>

UNIX Shell

Works with: bash

<lang bash>replace() {

   local search=$1 replace=$2
   local file lines line
   shift 2
   for file in "$@"; do
       lines=()
       while IFS= read -r line; do
           lines+=( "${line//$search/$replace}" )
       done < "$file"
       printf "%s\n" "${lines[@]}" > "$file"
   done

} replace "Goodbye London!" "Hello New York!" a.txt b.txt c.txt</lang>

Works with: ksh93

<lang bash>function replace {

   typeset search=$1 replace=$2
   typeset file lines line
   shift 2
   for file in "$@"; do
       lines=()
       while IFS= read -r line; do
           lines+=( "${line//$search/$replace}" )
       done < "$file"
       printf "%s\n" "${lines[@]}" > "$file"
   done

} replace "Goodbye London!" "Hello New York!" a.txt b.txt c.txt</lang>

VBScript

Works with: Windows Script Host version *

<lang VBScript> Const ForReading = 1 Const ForWriting = 2

strFiles = Array("test1.txt", "test2.txt", "test3.txt")

With CreateObject("Scripting.FileSystemObject") For i = 0 To UBound(strFiles) strText = .OpenTextFile(strFiles(i), ForReading).ReadAll() With .OpenTextFile(strFiles(i), ForWriting) .Write Replace(strText, "Goodbye London!", "Hello New York!") .Close End With Next End With </lang>

Vedit macro language

The list of files is in file "files.lst" which is expected to be in current directory. <lang vedit>File_Open("files.lst") // list of files to process

1. 20 = Reg_Free // text register for filename

While(!At_EOF) {

   Reg_Copy_Block(#20, Cur_Pos, EOL_Pos)
   File_Open(@(#20))
   Replace("Goodbye London!", "Hello New York!", BEGIN+ALL+NOERR)
   Buf_Close(NOMSG)
   Line(1, ERRBREAK)

}

Reg_Empty(#20) // Cleanup Buf_Quit(OK)</lang>

Wren

<lang ecmascript>import "io" for File

var files = ["file1.txt", "file2.txt"] for (file in files) {

   var text = File.read(file)
   System.print("%(file) contains: %(text)")
   text = text.replace("Goodbye London!", "Hello New York!")
   File.create(file) { |f|  // overwrites existing file
       f.writeBytes(text)
   }
   System.print("%(file) now contains: %(File.read(file))")

}</lang>

Output:

file1.txt contains: "Goodbye London!"

file1.txt now contains: "Hello New York!"

file2.txt contains: "Goodbye London!"

file2.txt now contains: "Hello New York!"

XPL0

<lang XPL0>include c:\cxpl\codes; \intrinsic 'code' declarations string 0; \use zero-terminated strings

func StrLen(A); \Return number of characters in an ASCIIZ string char A; int I; for I:= 0 to -1>>1-1 do

   if A(I) = 0 then return I;

func StrFind(A, B); \Search for ASCIIZ string A in string B \Returns address of first occurrence of string A in B, or zero if A is not found char A, B; \strings to be compared int LA, LB, I, J; [LA:= StrLen(A); LB:= StrLen(B); for I:= 0 to LB-LA do

   [for J:= 0 to LA-1 do
       if A(J) # B(J+I) then J:= LA+1;
   if J = LA then return B+I;  \found
   ];

return 0; ];

proc ReplaceText(FileName); \replace text in specified file char FileName; char Str(1_000_000), Hello, Bye, Pointer; int Handle, I, C; [Handle:= FOpen(FileName, 0); \get handle for input file FSet(Handle, ^I); \set device 3 input to file handle OpenI(3); \initialize buffer pointers I:= 0; repeat C:= ChIn(3); \read file into memory

       Str(I):= C;
       I:= I+1;

until C = $1A; \EOF FClose(Handle); \release handle

Hello:= "Hello New York!"; \replacement text Bye:= "Goodbye London!"; Pointer:= StrFind(Bye, Str); if Pointer \#0\ then \overwrite (both strings are same length)

  for I:= 0 to 15-1 do Pointer(I):= Hello(I);

Handle:= FOpen(FileName, 1); \get handle for output file FSet(Handle, ^O); \set device 3 output to file handle OpenO(3); I:= 0; repeat C:= Str(I); \write file from memory

       I:= I+1;
       ChOut(3, C);

until C = $1A; \EOF Close(3); \flush output buffer FClose(Handle); \release handle ];

int File, I; [File:= ["Alpha.txt", "Beta.txt", "Gamma.txt", "Delta.txt"]; for I:= 0 to 4-1 do ReplaceText(File(I)); ]</lang>

zkl

<lang zkl>fcn sed(data,src,dst){

  srcSz:=src.len(); dstSz:=dst.len(); md5:=Utils.MD5.calc(data);
  n:=0; while(Void!=(n:=data.find(src,n)))
          { data.del(n,srcSz); data.insert(n,dst); n+= dstSz; }
  return(md5!=Utils.MD5.calc(data)); // changed?

} fcn sedFile(fname,src,dst){

  f:=File(fname,"r"); data:=f.read(); f.close();
  if(sed(data,"Goodbye London!", "Hello New York!"))
     { f:=File(fname,"w"); f.write(data); f.close(); }

}</lang> This is a read file/blast it/write if changed. You could also do it line by line. <lang zkl>vm.arglist.apply2(sedFile); $ zkl bbb foo.txt bar.txt</lang> The apply2 method doesn't return anything, it is a side effects method. You could also easily thread this (by using sedFile.launch or sedFile.strand depending on if you wanted a true thread or a co-op thread). I didn't because I didn't want to bother with checking for duplicate files or file locking. vm.arglist, when passed to "main" (the constructor of the file being run) is a copy of argv that has been pruned.