supuner

supuner (SUPpress UNless ERror) executes a command and manipulates its stderr and stdout. By default, it captures both stderr and stdout and only outputs their combined value to stdout if command fails. supuner is useful for "chatty" commands whose output is only relevant if the command fails.

Usage

supuner [-e] [-o file] command [options ...]

Options:

• -e If -o is specified, then as well as sending output to a file, echo stdout and stderr combined to stdout.
• -o file Send stdout and stderr to file.

supuner exits with the exit code of command.

Examples

$ supuner ls /bin/sh
$ supuner ls /bin/sh /doesntexist
ls: /doesntexist: such file or directory
/bin/sh
$ supuner -o /tmp/o ls /bin/sh /doesntexist
$ echo $?
1
$ cat /tmp/o
ls: /doesntexist: such file or directory
/bin/sh
$ supuner -e -o /tmp/o ls /bin/sh /doesntexist
ls: /doesntexist: such file or directory
/bin/sh
$ echo $?
1
$ cat /tmp/o
ls: /doesntexist: such file or directory
/bin/sh

Using the fact that supuner exits with the exit code of command, one can use the || operator to perform actions on the combined stdout / stderr output, for example:

supuner -o /tmp/o ls /bin/sh /doesntexist >2 /dev/null \
  || mail -s 'Error from ls' somebody@example.com < /tmp/o