On Mon, Jan 16, 2012 at 09:25:30PM +0100, Andre Speelmans wrote: > I was not trying, the OP had a script that did a: > cat file | while read line; do something done > > Matthew commented that you should not rely on cat for reading a file > line by line and I was curious as to why not. ... I'm not aware of any particular reason not to use 'cat', and while it doesn't cost a lot, it's usually less expensive to use redirection. I just wanted to remind people that another way to redirect input (and output) is through the exec command. For instance: exec 0</usr/tmp/foo exec 1>/usr/tmp/bar exec 2>/usr/tmp/error while read INLINE do echo $INLINE done would read lines from file "/usr/tmp/foo" and output them to "/usr/tmp/bar", all within the shell. Moreover, any errors (should be none with something this simple, of course) would go to "/usr/tmp/error" as STDOUT. But wait! There's more! You can redirect to/from any numeric file descriptor. For instance: exec 3</usr/tmp/foo while read INLINE <&3 do echo $INLINE done would open file descriptor 3 on "/usr/tmp/foo", and the "while read" will walk through that file line by line. You can close descriptors in a script when done with them, e.g., exec 3>&- would close that descriptor opened in the above script snippet. Cheers, -- Dave Ihnat dihnat@xxxxxxxxxx -- users mailing list users@xxxxxxxxxxxxxxxxxxxxxxx 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
