How can I do something like this in bash?

if "`command` returns any error";
    echo "Returned an error"
    echo "Proceed..."

10 Answers 10


How to conditionally do something if a command succeeded or failed

That's exactly what bash's if statement does:

if command ; then
    echo "Command succeeded"
    echo "Command failed"

Adding information from comments: you don't need to use the [ ... ] syntax in this case. [ is itself a command, very nearly equivalent to test. It's probably the most common command to use in an if, which can lead to the assumption that it's part of the shell's syntax. But if you want to test whether a command succeeded or not, use the command itself directly with if, as shown above.

  • 31
    Note that the semicolon is important. Oct 17, 2011 at 7:37
  • 48
    Or you can just put then on a separate line.
    – l0b0
    Oct 17, 2011 at 9:00
  • 3
    Careful, this presumes the command``returns a sane return value. Today most do, but e.g. vi(1)` (the original one) was (in)famous for its random return values.
    – vonbrand
    Dec 27, 2015 at 21:02
  • 3
    @cgseller If you want to use multiple commands (like pipelines | or lists ;, &, &&, ||) between if and then you simply put them there like this: if ssh invalid | logger ; then echo "hi"; fi --- If you really want to enclose the command list once more you can use the curly {} or round () brackets. --- The construct $(ssh invalid | logger) is replaced by the stdout output of the command(s) (in this case the output of logger) and if the construct is in a place of a command (as in your example) then the substitued output is executed as a command. Dec 15, 2017 at 9:20
  • 3
    @DavidParks: command is just any arbitrary command, just as if you typed it by itself at the shell prompt. No, it doesn't need to be in backticks or $(...); that would be replaced by the output of the command (unless you want to execute a command given by the output of another command). For example: if cmp -s file1 file2 ; then echo Same ; else echo Different ; fi Jun 21, 2018 at 20:07

For small things that you want to happen if a shell command works, you can use the && construct:

rm -rf somedir && trace_output "Removed the directory"

Similarly for small things that you want to happen when a shell command fails, you can use ||:

rm -rf somedir || exit_on_error "Failed to remove the directory"

Or both

rm -rf somedir && trace_output "Removed the directory" || exit_on_error "Failed to remove the directory"

It's probably unwise to do very much with these constructs, but they can on occasion make the flow of control a lot clearer.

  • 6
    They are shorter and (at least in some shells) faster. I shudder remembering a monster Ultrix installation script written with just these conditional constructions I once tried to decipher...
    – vonbrand
    Dec 27, 2015 at 22:15
  • 4
    It should be noted that the order of && and || in the last example is important. If you reverse the order as in rm ... || command1 && command2, you'll end up executing both commands in case rm fails as here the && applies to command1 and assuming that doesn't fail as well, this will cause command2 to run. In the reverse order rm ... && command2 || command1 the double-excecution is not an issue, assuming command2 never fails.
    – Raven
    Mar 29, 2022 at 7:16
  • 2
    It is also noteworthy to know that if you need multiple commands, you can chain items in a subshell. This is almost always going to result in a spaghetti code situation and regular if statements should be used. But if needed you could run: command && (command1; command 2) || (command3; command 4) Aug 16, 2022 at 19:39

Check the value of $?, which contains the result of executing the most recent command/function:


echo "this will work"
if [ $RESULT -eq 0 ]; then
  echo success
  echo failed

if [ $RESULT == 0 ]; then
  echo success 2
  echo failed 2
  • 13
    While technically correct (and thus not warranting a downvote), it's not making use of Bash's if idiom. I prefer Keith Thompson's answer.
    – janmoesen
    Oct 17, 2011 at 11:30
  • 38
    There are benefits to this idiom -- it preserves the return value. In all, I find this one to be more powerful, though more verbose. it's also easier to read.
    – taxilian
    Oct 7, 2015 at 21:16
  • 7
    What is "Bash's if idiom"?
    – Nowaker
    Jun 27, 2016 at 1:37
  • 8
    @Nowaker The fact that the sole purpose of if is to do this. The flow control conditions in Bash all examine $? behind the scenes; that's what they do. Explicitly examining its value should be unnecessary in the vast majority of cases, and is usually a beginner antipattern.
    – tripleee
    Nov 4, 2016 at 12:34
  • 17
    I prefer this for readability. The main command is typically a really long one. Putting it inside an "if" statement makes for bad readability.
    – Nikhil VJ
    Sep 16, 2019 at 1:34

This worked for me:

command && echo "OK" || echo "NOK"

if command succeeds, then echo "OK" is executed, and since it's successful, execution stops there. Otherwise, && is skipped, and echo "NOK" is executed.

  • 6
    If you want to do something if it fails, and preserve the exit code (to show in command prompt or test in a script), you can do this: command && echo "OK" || c=$?; echo "NOK"; $(exit $c)
    – Sam Hasler
    Jun 24, 2014 at 15:57
  • 3
    @Sam-Hasler: shouldn't that be command && echo "OK" || (c=$?; echo "NOK"; (exit $c))?
    – jrw32982
    Apr 1, 2015 at 18:24
  • 17
    Also, if the echo "OK" part could itself fail, then this is better: command && (echo "OK"; exit 0) || (c=$?; echo "NOK"; (exit $c))
    – jrw32982
    Apr 1, 2015 at 18:34
  • @jrw32982, Nice, I've used the former construction, but not the latter.
    – Sam Hasler
    Apr 2, 2015 at 16:11
  • The real answer is in the comments, thanks all! Oct 24, 2017 at 20:13

It should be noted that if...then...fi and &&/|| type of approach deals with exit status returned by command we want to test( 0 on success ); however, some commands don't return a non-zero exit status if command failed or couldn't deal with input. This means that the usual if and &&/|| approaches won't work for those particular commands.

For instance, on Linux GNU file still exits with 0 if it received a non-existing file as argument and find couldn't locate the file user specified.

$ find . -name "not_existing_file"                                          
$ echo $?
$ file ./not_existing_file                                                  
./not_existing_file: cannot open `./not_existing_file' (No such file or directory)
$ echo $?

In such cases, one potential way we could handle the situation is by reading stderr/stdin messages, e.g. those that returned by file command, or parse output of the command like in find. For that purposes, case statement could be used.

$ file ./doesntexist  | while IFS= read -r output; do                                                                                                                  
> case "$output" in 
> *"No such file or directory"*) printf "%s\n" "This will show up if failed";;
> *) printf "%s\n" "This will show up if succeeded" ;;
> esac
> done
This will show up if failed

$ find . -name "doesn'texist" | if ! read IFS= out; then echo "File not found"; fi                                                                                     
File not found

The most error prone I could come up with was:

  • First, get the value. Suppose you do something like:


Now, for not only this situation, but others you may face, consider:

defined variable:

$ AA=1 ; if (( "10#0${AA}" == 1 )) ; then echo yes ; else echo no ; fi

Answer: yes

$ AA=1 ; if (( "10#0${AA}" != 1 )) ; then echo yes ; else echo no ; fi

Answer: no

undefined variable:

$ AA=1 ; if (( "10#0${BB}" == 1 )) ; then echo yes ; else echo no ; fi

Answer: no

$ AA=1 ; if (( "10#0${BB}" != 1 )) ; then echo yes ; else echo no ; fi

Answer: yes

$ AA=1 ; if (( "10#0${BB}" == 0 )) ; then echo yes ; else echo no ; fi

Answer: yes

This prevents all kinds off errors.

You are probably aware of all the syntax, but here some tips:

  • Use quotes. Avoid a "blank" to be nothing.
  • The new modern notation for variables is ${variable}.
  • Adding a zero concatenated before your number also avoid "no number at all".
  • But wait, adding a zero makes the number become base-8. You will get an error like:
    • value too great for base (error token is "08") for numbers above 7. That is when 10# comes into play:
    • 10# forces the number to be base-10.

You can do this:

if ($( ping -c1 > /dev/null )) ; then
  echo "ping response succsess!!!"
  • 12
    That works but is convoluted. You're running ping in a subshell of a subshell, the output of ping is captured in view of running it as a command. But because the output is redirected to /dev/null that will always be the empty string. So you're running nothing in a subshell, which means the previous exit status (of the command substitution subshell, that is of ping) will be retained. Obviously, the correct way is if ping ...; then here. Apr 1, 2015 at 15:40

if command-1 ; then
   echo "command-1 succeeded and now running from this block command-2"
   echo "command-1 failed and now running from this block command-3"

As noted elsewhere in this thread, the original question basically answers itself. Here is an illustration showing that if conditions may also be nested.

This example uses if to check if a file exists and if it is a regular file. If those conditions are true, then check whether or not it has a size greater than 0.


echo "Which error log are you checking today? "
read answer

if [ -f /opt/logs/$answer*.errors ]
        if [ -s /opt/logs/$answer*.errors ]
                echo "Content is present in the $answer error log file."
                echo "No errors are present in the $answer error log file."
        echo "$answer does not have an error log at this time."
  • 2
    That is what your answer does, but your answer does not address the question.
    – Jeff Schaller
    Dec 24, 2015 at 2:47
  • @JeffSchaller, thank you for your note. I edited my post to include a reference to the question. Dec 27, 2015 at 21:00

This could be done simply in this way as $? gives you the status of last command executed.

So it could be


... some command ...

if [ $? == 0 ] ; then
  echo '<the output message you want to display>'
  echo '<failure message>'
  • 1
    Downvote: This simply paraphrases an earlier answer which has rightfully received criticism for being unidiomatic.
    – tripleee
    Nov 4, 2016 at 12:35
  • Actually this was exactly what I was looking for because I'm trying to make the "command" fail the script as part of "set -e" which it doesn't if it's part of the if. This shouldn't be downvoted.
    – McTrafik
    Jan 12, 2021 at 1:15

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