Question

I have trawled the internet for this answer, but alas couldn’t find one.

In PHP I can run a command inside an if block, like so

if(command(blah)) {} else {}

As each function will return a truthy/falsey value. Can I do the same in a shell script? I want to echo output based on whether a command runs correctly. The commend to run is:

find . -type d -exec sudo chmod -R 775 {} \\;

I want to output that it ran successfully, or failed, then move on to another command.

Could I run the command into a variable or something similar?

Answer 1

Shell commands typically return an exit code indicating success or failure, with 0 indicating success and anything else indicating some sort of error (the specifics will depend on what command you’re running).

You can test for this exit code in an if statement:

if my_command; then
  echo It worked.
fi

And you can also chain commands together using the || and && operators.

my_command && echo It worked.
my_command || echo It failed.

Your specific example with the find command is a little tricky. The chmod command might fail, but the find command will still complete “successfully”. Something like this might help:

find . -type d -exec sudo sh -c 'chmod -R 775 {} || echo "FAILED {}"' \;

This will print…

FAILED ./path/to/directory

…for any place it fails, so you could check the output. But I’m not sure that’s absolutely necessary. There are few situations where your command is going to fail: e.g., on a read-only filesystem, or possibly on an NFS mount.