Bash: run command2 if command1 fails

Question

I want to do something like this:

if cmd1 && cmd2
echo success
else
echo epic fail
fi

How should I do it?

Solution 1

These should do what you need:

cmd1 && cmd2 && echo success || echo epic fail

or

if cmd1 && cmd2; then
    echo success
else
    echo epic fail
fi

Solution 2

The pseudo-code in the question does not correspond to the title of the question.

If anybody needs to actually know how to run command 2 if command 1 fails, this is a simple explanation:

• cmd1 || cmd2: This will run cmd1, and in case of failure it will run cmd2
• cmd1 && cmd2: This will run cmd1, and in case of success it will run cmd2
• cmd1 ; cmd2: This will run cmd1, and then it will run cmd2, independent of the failure or success of running cmd1.

Solution 3

Petr Uzel is spot on but you can also play with the magic $?.

$? holds the exit code from the last command executed, and if you use this you can write your scripts quite flexible.

This questions touches this topic a little bit, Best practice to use $? in bash? .

cmd1 
if [ "$?" -eq "0" ]
then
  echo "ok"
else
  echo "Fail"
fi

Then you also can react to different exit codes and do different things if you like.

Comments

[Admin]

You're just missing the "then" keyword before the "echo success" command.

[Admin]

Hmmm; your pseudocode seems to ask a different question than the one in your title.....

[Admin]

Good resource for some shell scripting exit conditions pixelbeat.org/programming/shell_script_mistakes.html

[mlissner]

This works, but I'm confused why || doesn't look at the output of the first echo command.

[m3nda]

@mlissner, the if else expects to exit codes, 0 if the command where launched and 1 if where errors. Do not read at the output. Just try whoami && whoami && echo success || echo epic fail and now whoami && whoareyou && echo success || echo epic fail. I cant figure out what you mean by "doesn't look at the output of the first echo command"

[Kazim Zaidi]

@mlissner I think I got your question, but the answer is that echo command won't fail ever. That is, its return will be 0, i.e. truthy. So the condition that really matters is just cmd1 && cmd2