🚀 go-pugleaf

>                          ...suppose I want to sort a file
>and place the result in the same file without destroying it,

Doesn't 'sort' allow you to do this already in one easy step?

	sort -o<file> <samefile>

...or did I misunderstand the question?
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In article <2274@ns-mx.uiowa.edu> jlhaferman@l_cae07.icaen.uiowa.edu (Jeffrey Lawrence Haferman) writes:
>For example, suppose I want to sort a file and place the result in the same
>file without destroying it, e.g.
>   % sort file > tmp; mv tmp file

You can use "sort file -o file" for that particular problem.  (It's in the
man pages.)

In general, you have to find a suitable location to hold the file, then
mv it to the destination.  Buffering the entire file in RAM does not work
for large files.
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In article <1215@tardis.Tymnet.COM> jms@tardis.Tymnet.COM (Joe Smith) writes:
> In article <2274@ns-mx.uiowa.edu> jlhaferman@l_cae07.icaen.uiowa.edu (Jeffrey Lawrence Haferman) writes:
    [ how to sort a file and place output back into same file? ]
  [ sort -o file file works ]
> In general, you have to find a suitable location to hold the file, then
> mv it to the destination.

No, you don't.

  % ( rm file; foo > file ) < file

foo's input will point at the old file; its output will go into the new
file. If foo reads all its input early and close()s to indicate this,
the disk space for the original will immediately disappear, provided
that it had only one link. If it had several links then the others will
stay around, entirely unaffected.

(I think cp foo bar should work like ( rm -f bar; cat > bar ) < foo, so
that other links to bar won't be affected; but POSIX 1003.2 apparently
disagrees and has cp foo bar work like cat < foo > bar. Oh, well.)

---Dan

In article <8029:Sep903:04:5390@kramden.acf.nyu.edu> brnstnd@kramden.acf.nyu.edu (Dan Bernstein) writes:
>(I think cp foo bar should work like ( rm -f bar; cat > bar ) < foo, so
>that other links to bar won't be affected; but POSIX 1003.2 apparently
>disagrees and has cp foo bar work like cat < foo > bar. Oh, well.)
>
 Please don't ever implement 'cp' in the way you suggest.  Doing so would
change file ownership, group, and permissions, not to mention that it would
fail if the file is in directory for which you do not have write permission.
It also messes up multiple links and symbolic links to the file.

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  Neil W. Rickert, Computer Science               <rickert@cs.niu.edu>
  Northern Illinois Univ.
  DeKalb, IL 60115.                                  +1-815-753-6940