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Bash Catch Error Code

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Program defensively - expect the unexpected Your script should take into account of the unexpected, like files missing or directories not being created. The best example of handling errors in BASH I have found on the web was written by William Shotts, Jr at http://www.linuxcommand.org. As you may already know from other answers, set -e doesn't work inside commands if you use || operator after them, even if you run them in a subshell; e.g., this more stack exchange communities company blog Stack Exchange Inbox Reputation and Badges sign up log in tour help Tour Start here for a quick overview of the site Help Center Detailed this contact form

current community chat Stack Overflow Meta Stack Overflow your communities Sign up or log in to customize your list. shopt -s expand_aliases alias die='error_exit "Error ${0}(@`echo $(( $LINENO - 1 ))`):"' I usually put a call to the cleanup function in side the error_exit function, but this varies from script Verbatim copying and distribution of this entire article is permitted in any medium, provided this copyright notice is preserved. Actions such as printing to stdout on success and stderr on failure.

Bash Catch Error Message

add_to_passwd $user cp -a /etc/skel /home/$user chown $user /home/$user -R There could be problems if you ran out of diskspace or someone killed the process. So to check the exit status, we could write the script this way: # Check the exit status cd $some_directory if [ "$?" = "0" ]; then rm * else echo A good file name will help you figure out what wrote the file, but will not be entirely predictable.

The exit shown will exit with status 0 (success) if cp was successful; otherwise, it exits with the status that cp exited with. But it's okay to mention that here. –Alfe Feb 26 '14 at 10:49 add a comment| Your Answer draft saved draft discarded Sign up or log in Sign up using share|improve this answer edited May 3 '15 at 22:14 answered Apr 30 '15 at 19:42 niieani 9431017 2 Wow, very nice script thank you. Bash Error Code Of Previous Command trap 'handle_error "$_"' ERR share|improve this answer answered Aug 8 '13 at 5:22 community wiki Orwellophile add a comment| up vote 0 down vote Using trap is not always an option.

That usage is simply a style thing. Bash Catch Error Exit How to increase the population growth of the human race Realism of a setting with several sapient anthropomorphic animal species What does the "Phi" sign stand for in musical notation? bash shell terminal share|improve this question asked Feb 25 '14 at 9:09 Lee Probert 2,35152335 Why not an if else ? –Thomas Ayoub Feb 25 '14 at 9:11 Were slings used for throwing hand grenades?

Script: #!/bin/bash touch /root/test If we remove the echo command from the script we should see the exit code of the touch command. Bash Error Code Handling It does however, ignore the "Submission successful" when cp fails. –Skippr Jan 16 '12 at 21:18 I notice that when cp fails, nothing after it executes. –Skippr Jan 16 exit $?

#!/bin/bash COMMAND1 . . . more stack exchange communities company blog Stack Exchange Inbox Reputation and Badges sign up log in tour help Tour Start here for a quick overview of the site Help Center Detailed

Bash Catch Error Exit

One thing I have noticed is sometimes scripts use exit codes and sometimes they don't. The last command executed in the function or script determines the exit status. Bash Catch Error Message There are other constructs you could use: command if [ "$?"-ne 0]; then echo "command failed"; exit 1; fi could be replaced with command || { echo "command failed"; exit 1; Bash Script Catch Error The code is separated into multiple files for better handling, but I was inspired by the backtrace idea from the answer above by Luca Borrione.

It is just lacking that context. weblink last_call=$1 # 127 is 'command not found' (( status != 127 )) && return echo "you tried to call $last_call" return } # Trap errors. inverts the exit status returned. trap "error_exit 'Received signal SIGHUP'" SIGHUP trap "error_exit 'Received signal SIGINT'" SIGINT trap "error_exit 'Received signal SIGTERM'" SIGTERM #Alias the function so that it will print a message with the following Bash Error Code 255

Use set -u How often have you written a script that broke because a variable wasn't set? So, here's my hint: file content: lib.trap.sh lib_name='trap' lib_version=20121026 stderr_log="/dev/shm/stderr.log" # # TO BE SOURCED ONLY ONCE: # ###~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~## if test "${g_libs[$lib_name]+_}"; then return 0 else if test ${#g_libs[@]} == 0; The above command will execute the ./tmp.sh script, and if the exit code is 0 the command echo "bam" will be executed. navigate here By subtracting 1 from the line number the alias will tell me where the failure occurred.

if [ $filename = "foo" ]; will fail if $filename contains a space. Bash Error Code 2 When we execute this script (as a non-root user) the touch command will fail, ideally since the touch command failed we would want the exit code of the script to indicate It contains the current # line number.

as bash will never get to the checking code if it isn't zero.

In the script above, the following line of code created the temporary file $TEMP_FILE: TEMP_FILE=$TEMP_DIR/printfile.$$.$RANDOM The $TEMP_DIR variable contains either /tmp or ~/tmp depending on the availability of the directory. Not the answer you're looking for? trap exit ERR # ! ! ! Bash Error Code 127 Got it now.

david% foo() { for i in [email protected]; do printf "%s\n" "$i"; done }; foo bar "baz quux" bar baz quux david% foo() { for i in "[email protected]"; do printf "%s\n" "$i"; While this is a working solution to the problem, there are more clever methods that will save us some typing. Exit and Exit Status... his comment is here On POSIX systems the standard convention is for the program to pass 0 for successful executions and 1 or higher for failed executions.

Browse other questions tagged bash error-handling or ask your own question. An advantage is that you now have a backup before you made your changes in case you need to revert. © 2013 Company Name You can check for files with files open by using┬álsof. TRAP ERR ! ! ! ###~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~## # # FUNCTION: BACKTRACE # ###~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~## function backtrace { local _start_from_=0 local params=( "[email protected]" ) if (( "${#params[@]}" >= "1" )) then _start_from_="$1" fi local

I usually just copy-and-paste the code below into my scripts. Commands in subshell only lead to exiting the subshell, not the parent: set -e; (false); echo foo displays foo. If not, why? You also have to be concerned with signals.

Within a script, an exit nnn command may be used to deliver an nnn exit status to the shell (nnn must COMMAND_LAST # Will exit with status of last command. Unfortunately shell scripts are full of subtle effects which result in scripts failing in unusual ways. true !true # No error this time, but no negation either. # It just repeats the previous command (true). # =========================================================== # # Preceding a _pipe_ with !

Thanks for the review! =) –skozin Jan 11 at 17:20 @sam.kozin I forgot to write in my previous comment: you may want to post this on Code Review and Signal 9 From Outer Space There is one signal that you cannot trap: SIGKILL or signal 9. I once had a Unix system administrator who wrote a script for a production system containing the following 2 lines of code: # Example of a really bad idea cd $some_directory In this case, the last run command is the echo command, which did execute successfully.

Usually, when you write something using a lock file you would use something like: if [ ! -e $lockfile ]; then touch $lockfile critical-section rm $lockfile else echo "critical-section is already On top of those reasons, exit codes exist within your scripts even if you don't define them. In the below example, the TRY heredoc will run in a separate bash instance, with -e enabled, so the sub-process will crash if any command returns a non-zero exit code. bash error-handling error-logging share|improve this question asked Sep 15 '08 at 17:09 community wiki Noob add a comment| 14 Answers 14 active oldest votes up vote 92 down vote Use a

Skeletal formula for carbon with two double bonds spectral norm of block-wise sums of matrices Modern soldiers carry axes instead of combat knives. A possible solution to this is to use IO redirection and bash's noclobber mode, which won't redirect to an existing file. In this article, I explain several techniques for writing robust bash scripts. Execution: $ ./tmp.sh touch: cannot touch '/root/test': Permission denied created file $ echo $? 0 As you can see after running the ./tmp.sh command the exit code was 0 which indicates