Shell script?

D4ve G · 02-14-2009, 10:53 AM

How to I tell in a shell script if a command is valid or not?

For example if the user typed

./MyScript ls

How could I check 'ls' if ls existed or not?

unSpawn · 02-14-2009, 11:19 AM

The test for "exists" is "-e" like in: '[ -e "$1" ] || echo {doesnt exist.; exit 1; }'.

jlinkels · 02-14-2009, 11:29 AM

better is

Code:

if [ -x file ]

which indicates that the file exists but that it is also an executable file.

(That wasn't that hard to find in Google!)

jlinkels

colucix · 02-14-2009, 11:34 AM

The argument must have the full path of the executable, otherwise the test fails. Better to use the which command.

D4ve G · 02-15-2009, 09:56 AM

Quote:

Originally Posted by colucix

The argument must have the full path of the executable, otherwise the test fails. Better to use the which command.

I got it working for some some commands but not all.
Which sometimes only returns the path but sometimes it returns more.

Example:
ls: aliased to /usr/bin/ls -CF

unSpawn · 02-15-2009, 10:07 AM

Quote:

Originally Posted by D4ve G

Which sometimes only returns the path but sometimes it returns more.

See 'which --skip-alias --skip-functions' ?

D4ve G · 02-15-2009, 10:18 AM

Quote:

Originally Posted by unSpawn

See 'which --skip-alias --skip-functions' ?

Not sure if I'm stupid or what but I can't find any flags for which.

jlinkels · 02-15-2009, 10:39 AM

If you want to use 'which', use the last function result: 0 for one or more executables found, 1, 2: no executable found.

Code:

donald_pc:~$ which bash
/bin/bash
donald_pc:~$ echo $?
0
donald_pc:~$ which pietje
donald_pc:~$ echo $?
1

jlinkels

colucix · 02-15-2009, 12:18 PM

Quote:

Originally Posted by D4ve G

Not sure if I'm stupid or what but I can't find any flags for which.

Have you tried them? Did you receive some error about invalid option? Anyway, I would stick with jlinkels' solution:

Code:

if which $command > /dev/null 2>&1
then
  echo "Command $command exists!"
fi

And... Happy Birthday to you!!