On 12 Jan 2012 14:13:53, Anthony R Fletcher wrote: > On 12 Jan 2012 at 14:02:50, Dean S. Messing wrote: > > > > In a system script I find this snippet > > > > nodevs=$(< /proc/filesystems fgrep rootfs) > > > > and don't understand the syntax. According to the bash man page, > > > > $(< file) is shorthand for $(cat file). But then the above should read > > > > nodevs=$(< /proc/filesystems | fgrep rootfs) > > > > However, the latter leaves $nodevs empty whereas the former puts the > > stuff that fgrep processes into nodevs as it should. > > > The command > < /proc/filesystems fgrep rootfs > > redirects the input from the file /proc/filesystems into the command > "fgrep rootfs". You could rewrite this as > fgrep rootfs < /proc/filesystems > > nodevs=$( command ) takes the result of the command inside the > parentheses and assigns into the variable nodevs.
Ahh! A perfect explanation. Thanks. I did not realise (or, rather, think about) trying the entire command w/in $(...) on the commandline. The manpage says $(< file) is equivalent to $(cat file), so I made the mathematically naive assumption that "< file" is equivalent to "cat file". When "< file" didn't act like "cat file" on the commandline (which I did try) I became confused. Dean -- users mailing list users@lists.fedoraproject.org To unsubscribe or change subscription options: https://admin.fedoraproject.org/mailman/listinfo/users Guidelines: http://fedoraproject.org/wiki/Mailing_list_guidelines Have a question? Ask away: http://ask.fedoraproject.org
