Readline interface
A readline interface is a line editing facility that provides auto completion facilities and the ability to recall previously typed lines. Build a simple application that accepts at least two commands and uses a readline style interface.
The interface should provide
- the ability to recall previously typed commands
- commandline editing
- application specific commands
The application could be based on Simple database or something else.
If the language already provides a readline interface, then it should be demonstrated how build an application specific readline interface (one that only understands the applications commands) and also show how to customize the builtin readline to provide the above features and especially add application specific commands.
See also: Input loop
C
A program that does absolutely nothing. Type 'help' for help. <lang c>#include <readline/readline.h>
- include <readline/history.h>
- include <string.h>
int main() { char *s; using_history(); while (1) { s = readline("This be a prompt> ");
if (!s || !strcmp(s, "quit")) { puts("bye."); return 0; }
if (!strcmp(s, "help")) puts("commands: ls, cat, quit"); else if (!strcmp(s, "ls") || !strcmp(s, "cat")) { printf("command `%s' not implemented yet.\n", s); add_history(s); } else puts("Yes...?"); } }</lang>
PARI/GP
gp uses readline, but it can also be used directly in PARI:
<lang c>#include <stdio.h>
- include <pari/pari.h>
- include <readline/readline.h>
- include <setjmp.h>
jmp_buf env; void gp_err_recover(long numerr) { longjmp(env, numerr); }
/* History handling (%1, %2, etc.)*/ pari_stack s_history; GEN *history; GEN parihist(long p) {
if (p > 0 && p<=s_history.n) return history[p-1]; else if (p<=0 && s_history.n+p-1>=0) return history[s_history.n+p-1]; pari_err(talker,"History result %ld not available [%%1-%%%ld]",p,s_history.n); return NULL; /* not reached */
}
int main(int argc, char **argv) {
char *in, *out;
GEN z;
entree hist={"%",0,(void*)parihist,13,"D0,L,","last history item."};
printf("Welcome to minigp!\n");
pari_init(8000000,500000);
cb_pari_err_recover = gp_err_recover;
pari_add_function(&hist);
stack_init(&s_history,sizeof(*history),(void**)&history);
(void)setjmp(env);
while(1)
{
in = readline("? ");
if (!in) break;
if (!*in) continue;
z = gp_read_str(in);
stack_pushp(&s_history,(void*)gclone(z)); /*Add to history */
out = GENtostr(z);
printf("%%%ld = %s\n",s_history.n,out);
free(in); free(out); avma=top;
}
return 0;
}</lang>
Code thanks to Bill Allombert
Pike
watch.pike is the solution from Simple database#Pike. this solution demonstrates how to retrofit an application with a readline interface by inheriting the original and overriding specific functions.
<lang pike>#!/usr/bin/pike
inherit "watch.pike";
Stdio.Readline readln = Stdio.Readline();
void print_help() {
write("The following commands are available: \n");
write(sort(indices(functions))*", ");
write("\n");
}
void watch_add() {
::watch_add(db);
}
void watch_list() {
::watch_list(db);
}
void do_exit() {
exit(0);
}
mapping functions = ([ "add":watch_add,
"list":watch_list,
"load":watch_load,
"save":watch_save,
"help":print_help,
"quit":do_exit ]);
string prompt_read(string prompt) {
return readln->read(prompt+": ");
}
void main() {
Stdio.Readline.History readline_history = Stdio.Readline.History(512); readln->enable_history(readline_history);
string prompt="> ";
print_help();
while(1)
{
string input=readln->read(prompt);
if(!input)
exit(0);
if(input != "")
{
if (functions[input])
functions[input]();
else
{
write("unknown command\n");
print_help();
}
}
}
}</lang>
Sample session:
pike watch_rl.pike The following commands are available: add, help, list, load, quit, save > load > list Rosetta Code 2 Simple Database (27.10.2011.) > add Series: Rdm asks! Title: Balanced ternary Episode: 1 Date watched: 1.11.2011 Add new series? [y/n]: : y > list Rdm asks! 1 Balanced ternary (1.11.2011.) Rosetta Code 2 Simple Database (27.10.2011.) > hello unknown command The following commands are available: add, help, list, load, quit, save > save > quit
Racket
Racket's has a readline interface which is not used by default due to its license. This includes the usual readline-style editing, and tab-completion for Racket bindings. It is possible to use it as a library, or as a REPL convenience (both uses described in the documentation) -- but it is better to use xrepl which provides an enhanced command-line REPL and includes the readline interaction.
REXX
This REXX programs supports a REDO (re-do) with very limited editing to keep the program simple.
It has a history (which can be interrogated) and some of the simple (MS) DOS commands.
The HELP (?), REDO, error checking, and abbreviations took up most of the program.
"User" commands (subroutines) are identified with a leading period (.) to make it easier to understand what's what.
<lang rexx>/*REXX program to implement a simple "readline" shell. */
trace off /*suppress echoing of non-zero RC*/
signal on syntax; signal on novalue /*handle REXX program errors. */
cmdX='ATTRIB CAL CHDIR COPY DEL DIR ECHO EDIT FC FIND KEDIT LLL',
'MEM MKDIR MORE REM REXX RMDIR SET TYPE VER XCOPY'
cls='CLS' /*define the pgm to clear screen.*/ @hist.='*** command not defined. ***' /*initialize the history database*/ hist#=0 /*number of commands in history. */ prompt='Enter command ──or── ? ──or── Quit' /*default PROMPT msg.*/ sw=linesize() /*some REXX don't have this BIF. */ cls /*start with a clean slate. */ redoing=0 /*flag for executing naked ReDO.*/
do forever /*do it until the fat lady sings.*/ if prompter() then iterate /*Nothing entered? So try again.*/ select /*now then, let's rock & roll. */ when wordpos(xxxF,cmdX)\==0 then call .cmdX when xxxF=='EXIT' | xxxF="QUIT" then leave /*the fat lady sung.*/ when xxxF=='HISTORY' then call .history when xxxF=='HELP' then call .help when xxxF=='PROMPT' then call .prompt when xxxF=='REDO' then call .redo otherwise call er 'unknown command:' xxx yyy end /*select*/ end /*forever*/
say xxxF'ting...' /*say goodbye, 'cause it's polite*/ exit /*stick a fork in it, we're done.*/ /*───────────────────────────────error handling subroutines and others.─*/ er: say; say; say '****error!****'; say; say arg(1); say; say; return err: say; say; say center(' error! ',max(40,linesize()%2),"*"); say
do j=1 for arg(); say arg(j); say; end; say; exit 13
novalue: syntax: call err 'REXX program' condition('C') "error",,
condition('D'),'REXX source statement (line' sigl"):",,
sourceline(sigl)
/*──────────────────────────────────.CMDX subroutine────────────────────*/ .cmdX: xxxF yyy; return /*──────────────────────────────────.HELP subroutine────────────────────*/ .help: cmdsH='ATTRIB CHDIR CLS COPY DEL DIR ECHO EDIT FC FIND MEM',
'MKDIR MORE PRINT REM RMDIR SET TREE TYPE VER XCOPY'
/*the above commands have their own help via /? */
cmds='?|Help|MANual ATTRIButes CALendar CD|CHDIR|CHANGEDir COPY DELete|ERASE',
'DELete|ERASE DIR ECHO EDIT FC|FILECOMPAre FIND HISTory Kedit LLL',
'MEM MD|MKDIR|MAKEDir MORE PRINT PROMPT Quit|EXIT',
'R4 RD|RMDIR|REMOVEDir REGINA REMark Rexx REDO SET TREE Type VER'
say center(strip(xxx yyy),sw-1,'═'); cmds_=cmds; yyyF=unabbrev(yyy)
help. = ' No help is available for the' yyy "command." help.cal = 'shows a calendar for the current month or specified month.' help.kedit = 'KEDITs the file specified.' help.lll = 'shows a formatted listing of files in the current directory.' help.prompt= 'sets the PROMPT message to the specified text.' help.quit = 'quits (exits) this program.' help.redo = 're-does the command # specified (or the last command).' help.rexx = 'executes the REXX program specified.'
if yyy== then do j=1 while cmds_\==
parse var cmds_ x cmds_
say left(,sw%2) changestr('|',x," | ")
end /*j*/
else select
when wordpos(yyyF,cmdsH)\==0 then yyyF '/?'
otherwise cmd?=yyyF
if left(help.yyyF,1)\==' ' then say yyyF ' ' help.yyyF
else say help.yyyF
end /*select*/
return /*──────────────────────────────────.HISTORY subroutine─────────────────*/ .history: say center('history',sw-1,'═'); w=length(hist#)
do j=1 for hist#
say right(j,w) '===>' @hist.j
end /*j*/
return /*──────────────────────────────────.PROMPT subroutine──────────────────*/ .prompt: if yyyU\== then prompt=yyy; return /*──────────────────────────────────PROMPTER subroutine─────────────────*/ prompter: if redoing then do /*special case for naked REDO */
redoing=0; z=hist#-1
parse var @hist.z xxx yyy
end
else do
if prompt\== then do; say; say prompt; end
parse pull xxx yyy
end
xxxU=xxx; upper xxxU; if xxx== then return 1 /*No input? Try again*/ yyyU=yyy; upper yyyU; yyyU=strip(yyyU) hist#=hist#+1; /*bump the history counter. */ @hist.hist#=strip(xxx yyy) /*assign to history. */ xxxF=unAbbrev(xxx) /*expand the abbreviation (maybe)*/ return 0 /*──────────────────────────────────.redo subroutine────────────────────*/ .redo:
select when yyyU== then redoing=1 /*assume they want the last cmd. */ when words(yyy)\==1 then call er 'too many args specified for' xxx when \datatype(yyy,'W') then call er "2nd arg isn't numeric for" xxx otherwise nop end /*select*/
if redoing then return /*handle with kid gloves. */ yyy=yyy/1 /*normalize it: +7 7. 1e1 007 7.0*/ say 'Re-doing:' @hist.yyy @hist.yyy return /*──────────────────────────────────UNABBREV subroutine─────────────────*/ unabbrev: procedure; arg ccc
select
when abbrev('ATTRIBUTES',ccc,6) then return 'ATTRIB'
when abbrev('CALENDAR',ccc,3) then return 'CAL'
when abbrev('CHANGEDIR',ccc,7) |,
ccc=='CHDIR' |,
ccc=='CD' then return 'CHDIR'
when abbrev('CLEARSCREEN',ccc,5) then return 'CLS'
when abbrev('FILECOMPARE',ccc,9) then return 'FC'
when abbrev('DELETE',ccc,3) |,
ccc=='ERASE' then return 'DEL'
when abbrev('HISTORY',ccc,4) then return 'HISTORY'
when abbrev('HELP',ccc,1) |,
abbrev('MANUAL',ccc,3) |,
ccc=='?' then return 'HELP'
when abbrev('MAKEDIR',ccc,5) |,
ccc=='MKDIR' |,
ccc=='MD' then return 'MKDIR'
when abbrev('KEDIT',ccc,1) then return 'KEDIT'
when abbrev('QUIT',ccc,1) then return 'QUIT'
when abbrev('REMARK',ccc,3) then return 'REM'
when abbrev('REMOVEDIR',ccc,7) |,
ccc=='RMDIR' |,
ccc=='RD' then return 'RMDIR'
when abbrev('REXX',ccc,1) then return 'REXX'
when abbrev('TYPE',ccc,1) then return 'TYPE'
otherwise nop
end /*select*/
return ccc</lang>
This REXX program makes use of LINESIZE REXX program (or BIF) which is used to determine the screen width (or linesize) of the terminal (console).
The LINESIZE.REX REXX program is included here ──► LINESIZE.REX.
Some older REXXes don't have a changestr BIF, so one is included here ──► CHANGESTR.REX.
output showing a sample session
Enter command ──or── ? ──or── Quit
hel
═══════════════════════════════════════════hel══════════════════════════════════
? | Help | MANual
ATTRIButes
CALendar
CD | CHDIR | CHANGEDir
COPY
DELete | ERASE
DELete | ERASE
DIR
ECHO
EDIT
FC | FILECOMPAre
FIND
HISTory
Kedit
LLL
MEM
MD | MKDIR | MAKEDir
MORE
PRINT
PROMPT
Quit | EXIT
R4
RD | RMDIR | REMOVEDir
REGINA
REMark
Rexx
REDO
SET
TREE
Type
VER
Enter command ──or── ? ──or── Quit
rexx $mayan 123,456,787,654,321
╔════╗ ╔════╗ ╔════╗ ╔════╗ ╔════╗ ╔════╗ ╔════╗ ╔════╗ ╔════╗ ╔════╗ ╔════╗
║ ║ ║ ║ ║ ║ ║ ║ ║ ║ ║ ║ ║ ║ ║ ∙ ║ ║ ║ ║ ∙ ║ ║ ║
║ ∙∙ ║ ║ ║ ║ ║ ║ ║ ║ ∙∙ ║ ║ ║ ║ ║ ║────║ ║────║ ║────║ ║ ║
║────║ ║ ║ ║ ║ ║────║ ║────║ ║ ∙ ║ ║ ║ ║────║ ║────║ ║────║ ║ ║
║────║ ║ ∙ ║ ║ ∙∙ ║ ║────║ ║────║ ║────║ ║ ∙∙ ║ ║────║ ║────║ ║────║ ║ ∙ ║
╚════╝ ╚════╝ ╚════╝ ╚════╝ ╚════╝ ╚════╝ ╚════╝ ╚════╝ ╚════╝ ╚════╝ ╚════╝
Enter command ──or── ? ──or── Quit
cal
┌────────────────────────────────────────────────────────────────────────────┐
│ │
│ │
│ June 2012 │
│ │
│ │
│ Sunday Monday Tuesday Wednesday Thursday Friday Saturday │
├──────────┬──────────┬──────────┬──────────┬──────────┬──────────┬──────────┤
│ │ │ │ │ │ │ │
│ │ │ │ │ │ │ │
│ │ │ │ │ │ ─ 1 ─ │ 2 │
│ │ │ │ │ │ │ │
│ │ │ │ │ │ │ │
├──────────┼──────────┼──────────┼──────────┼──────────┼──────────┼──────────┤
│ │ │ │ │ │ │ │
│ │ │ │ │ │ │ │
│ 3 │ 4 │ 5 │ 6 │ 7 │ 8 │ 9 │
│ │ │ │ │ │ │ │
│ │ │ │ │ │ │ │
├──────────┼──────────┼──────────┼──────────┼──────────┼──────────┼──────────┤
│ │ │ │ │ │ │ │
│ │ │ │ │ │ │ │
│ 10 │ 11 │ 12 │ 13 │ 14 │ 15 │ 16 │
│ │ │ │ │ │ │ │
│ │ │ │ │ │ │ │
├──────────┼──────────┼──────────┼──────────┼──────────┼──────────┼──────────┤
│ │ │ │ │ │ │ │
│ │ │ │ │ │ │ │
│ 17 │ 18 │ 19 │ 20 │ 21 │ 22 │ 23 │
│ │ │ │ │ │ │ │
│ │ │ │ │ │ │ │
├──────────┼──────────┼──────────┼──────────┼──────────┼──────────┼──────────┤
│ │ │ │ │ │ │ │
│ │ │ │ │ │ │ │
│ 24 │ 25 │ 26 │ 27 │ 28 │ 29 │ 30 │
│ │ │ │ │ │ │ │
│ │ │ │ │ │ │ │
└──────────┴──────────┴──────────┴──────────┴──────────┴──────────┴──────────┘
Enter command ──or── ? ──or── Quit
LLL
mm/dd/yyyy hh:mm ──filesize── ─────────────────filename D:\*.*─────────────────
06/01/2012 10:36 2,322 DIV_GRID.TXT
05/13/2012 20:39 1,044 MOD_EXP.REX
05/13/2012 19:39 694 MOD_EXP.TXT
06/01/2012 02:32 1,439 RCOMBN.RX_
06/01/2012 02:24 7,181 READLINT.REX
05/29/2012 22:48 60 sub00.REX
──────────────────────12,740 <──────────────total bytes [6 files]
Enter command ──or── ? ──or── Quit
dir
Volume in drive D is -----D-----
Volume Serial Number is 68D0-6356
Directory of D:\
05/09/2012 12:40 <DIR> Config.Msi
12/16/2005 19:54 <DIR> Documents and Settings
01/15/2006 10:33 <DIR> Program Files
04/14/2010 19:58 <DIR> Recycled
12/16/2005 20:29 <DIR> System Volume Information
01/26/2011 00:21 <DIR> temp
12/16/2005 19:42 <DIR> WINDOWS
01/06/2006 14:43 211 boot.ini
06/01/2012 10:36 2,322 DIV_GRID.TXT
12/16/2005 20:18 0 IO.SYS
05/13/2012 20:39 1,044 MOD_EXP.REX
05/13/2012 19:39 694 MOD_EXP.TXT
12/16/2005 20:18 0 MSDOS.SYS
08/04/2004 12:00 47,564 NTDETECT.COM
08/04/2004 12:00 250,032 ntldr
06/01/2012 02:32 1,439 RCOMBN.RX_
06/01/2012 02:24 7,181 READLINT.REX
05/29/2012 22:48 60 sub00.REX
11 File(s) 310,547 bytes
7 Dir(s) 6,793,314,304 bytes free
Enter command ──or── ? ──or── Quit
help ver
════════════════════════════════════════help ver═════════════════════════════════════════
Displays the Windows XP version.
VER
Enter command ──or── ? ──or── Quit
ver
Microsoft Windows XP [Version 5.1.2600]
Enter command ──or── ? ──or── Quit
q
QUITting...