View Source: SpacesInPathNames - Waikato Linux Users Group

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Unix/Linux allows any character in a file/directory name except __/__ or __[NUL]__. However, embedded spaces, newlines and the like can cause problems for carelessly-written [Shell] scripts (or scripts for [carelessly-written shells|CshProgrammingConsideredHarmful]), and cause some command [PipeLine]s to fail completely.

To get around this, the [GNU] versions of find(1) and xargs(1) incorporate special extensions that work together. The __-print0__ option to __find__ causes it to output matching pathnames terminated by __NUL__ characters rather than newlines, thereby avoiding confusion with any embedded newlines that might occur in the pathnames. Correspondingly, the __xargs__ command takes the option __--null__ (shorter synonym __-0__) to indicate that its input is delimited in this way; though on my [SUSE] system I also have to specify __--max-lines=1__ (shorter synonym __-L1__).

For instance, suppose I have the following files:

  <pre>
  Events/Weddings/Freda's Wedding/data.txt
  Events/Car Race/data.txt
  Events/New Year Fireworks/data.txt
  </pre>

and I want to count up the number of lines in each "data.txt" file. I can do this as follows:

  <pre>
  find Events -name data.txt -print0 | xargs -0 -L1 wc -l
  </pre>

----
As discussed on the BashNotes page, scripts can cope with arguments that contain spaces if you are careful. <tt>bash</tt> will expand *$@* as all of its arguments, but importantly will expand *"$@"* as each argument surrounded by "quote marks". Eg, if a script is called with arguments
<verbatim>
 ./myscript "argument 1" "argument 2"
</verbatim>
then a script that did
<verbatim>
  perl -e 'foreach $a (@ARGV) {print ".$a.\n"}' $@
</verbatim>
would output
<verbatim>
.argument.
.1.
.argument.
.2.
</verbatim>
while a script that did
<verbatim>
  perl -e 'foreach $a (@ARGV) {print ".$a.\n"}' "$@"
</verbatim>
would output
<verbatim>
.argument 1.
.argument 2.
</verbatim>

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Last edited on Wednesday, March 22, 2006 5:36:20 pm by LawrenceDoliveiro

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