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OSXFAQ Mac OS X UNIX Tip-of-the-Day
Scripting One-Liners - Bulk Redirection
We all know how to redirect output to a file using the redirection symbol '>'.
$ ls > file-list
Here's an example in which we redirect the output of many commands in a shell script, and without having to redirect the output of each command individually. Create a sub-shell around the commands who's output you wish to redirect.
$ (
>ls
>df
>cat number-list
>) > out
$
You can use a group-command instead of a sub-shell by replacing
(...) > out
with
{...} > out
Use the same trick to re-direct standard input to a group of commands.
$ cat infile
1234
full
$ { read code; read membership; } < infile
$ echo $code $membership
1234 full
$
Note: use a group-command, not a sub-shell, if you wish to retain the values of variables. A sub-shell is executed by a new instance of the shell, and its environment (including all variable) dies when the sub-shell completes.
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