From: Brian Foster (blf at domain utvinternet.ie)
Date: Tue 30 Apr 2002 - 10:11:44 IST
| Date: Tue, 30 Apr 2002 02:41:31 +0100
| From: Niall O Broin <niall at domain linux.ie>
| Take the trivial bash script shown which I'll call echo.sh
| echo $1
| and pass it an argument with spaces in e.g.
| echo.sh "a b c d"
| and the output will be
| a b c d
| i.e. all the repeated spaces are compressed to one space.
| [ needs spaces preserved ... ]
you'll get lots of replies to this...!
answer . . . quote it:
rationale . . in this context, the quotes inform the shell the
substitution is remain a single word, rather than
being broken up into its constituent words; i.e.,
this is a feature of all Bourne-ish shells, not a
bug per se.
warning . . . depending on too many conditions (see bash(1)),
echo 'foo\nbar' may produce either:
which can be, and has been, used to crack systems.
trivia note . actually, it's the first character of IFS which is
used to separate constituent words, so, with some
limitations, a completely off-the-wall answer is:
IFS="" # i.e., nothing (empty)
IFS=$old # restore previous IFS
it is left as an exercise to the reader why I do
not need to quote the right-hand-side of any of
the assignments made above (the one time I did
redundantly use quotes was merely for emphasis).
-- Innovative, very experienced, Unix and | Brian Foster Dublin, Ireland Chorus (embedded RTOS) kernel internals | e-mail: blf at domain utvinternet.ie expert looking for a new position ... | mobile: (+353 or 0)86 854 9268 For a resume, contact me, or see my website http://www.blf.utvinternet.ie
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