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Truncate a file: Difference between revisions
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→{{header|REXX}}: changed/added comments and whitespace.
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::::* then erased (deleted),
::::* then written to.
<lang rexx>/*REXX program truncates a file to a specified (and smaller) number of bytes. */
parse arg siz FID /*
FID=strip(FID) /*elide FID leading/trailing blanks.
if siz=='' then call ser "No truncation size was specified (1st argument)."
if FID=='' then call ser "No fileID was specified (2nd argument)."
if \datatype(siz,'W') then call ser "trunc size isn't an integer: " siz
if siz<1 then call ser "trunc size isn't a positive integer: " siz
_=charin(FID,1,siz+1) /*position file and read a wee bit more*/
#=length(_) /*get the length of the part just read.*/
if #==0 then call ser "the specified file doesn't exist: " FID
if #<siz then call ser "the file is smaller than trunc size: " #
call lineout FID /*close the file used, just to be safe.*/
'ERASE' FID /*invoke a command to delete the file */
call lineout FID /*close the file, maybe for REXX's use.*/
call charout FID, left(_,siz), 1 /*write a truncated version of the file*/
call lineout FID /*close the file used, just to be safe.*/
say 'file '
exit /*stick a fork in it, we're all done. */
/*──────────────────────────────────────────────────────────────────────────────────────*/
ser: say '***error
For this example, Windows/XP and Windows 7 operating systems were used, the program was tested with:
:::* Personal REXX
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===with memory constraints===
<lang rexx>/*REXX program truncates a file to a specified (and smaller) number of bytes. */
parse arg siz FID /*
FID=strip(FID) /*elide FID leading/trailing blanks.
if siz=='' then call ser "No truncation size was specified (1st argument)."
if FID=='' then call ser "No fileID was specified (2nd argument)."
if \datatype(siz,'W') then call ser "trunc size isn't an integer: " siz
if siz<1 then call ser "trunc size isn't a positive integer: " siz
chunk=4000 /*read the file with this "buffer" size*/
call charin fid,1,0 /*position the file pointer to byte # 1*/
_= /* [↓] read while the length data<siz.*/
do while length(_)<=siz /* [↓] have we reached End-Of-File ? */
buffer=charin(FID,,chunk)
if #==0 then call ser "the specified file doesn't exist: " FID
if #<siz then call ser "the file is smaller than trunc size: " #
call lineout FID /*close the file used, just to be safe.*/
'ERASE' FID /*invoke a command to delete the file */
call lineout FID /*close the file, maybe for REXX's use.*/
call charout FID, left(_,siz), 1 /*write a truncated version of the file*/
call lineout FID /*close the file used, just to be safe.*/
say 'file '
exit /*stick a fork in it, we're all done. */
/*──────────────────────────────────────────────────────────────────────────────────────*/
ser: say '***error
'''output''' is identical to the 1<sup>st</sup> REXX version. <br><br>
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