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Bash Script Set Error


I think this should have been the default behavior: since such errors almost always signify something unexpected, it is not really 'sane' to keep executing the following commands. By the way, my hapless system administrator's script suffered this very failure and it destroyed a large portion of an important production system. I like to include the name of the program in the error message to make clear where the error is coming from. if [ -d "$1" ] then printf "${green}${NC}\\n" "$1" cd -- "$1" else printf "${red}${NC}\\n" "$1" fi But if your purpose is to silence the possible errors then cd -- "$1" navigate here

Perhaps a safer option is to decide never to use short-circuiting at all, and always use full if-statements instead. I know I have, many times. This may be exactly the behavior you want. If IFS is more than one character, splitting will be done on any of those characters.

Bash Script Set Variable

asked 6 years ago viewed 69579 times active 6 years ago Linked 276 Automatic exit from bash shell script on error 192 What does set -e mean in a bash script? With these settings, certain common errors will cause the script to immediately fail, explicitly and loudly. asked 2 years ago viewed 25523 times active 8 months ago Related 5Is it possible to get the error message from previous command which failed when the conditional command runs using Aborting." fi AND and OR lists Finally, we can further simplify our script by using the AND and OR control operators.

  • While this is a working solution to the problem, there are more clever methods that will save us some typing.
  • What are the holes on the sides of a computer case frame for?
  • Since cd returns a non-zero status on failure, you could do: cd -- "$1" && echo OK || echo NOT_OK You could simply exit on failure: cd -- "$1" || exit
  • echo '--> cleanup' return $exit_code } echo '<-- outer' } inner() { set -e echo '--> inner' some_failed_command echo '<-- inner' } outer But || operator is needed to prevent returning

Didn't know about Code Review. –skozin Jan 11 at 17:27 add a comment| up vote 2 down vote To expand on the @Gilles' answer: Indeed, set -e doesn't work inside commands Be atomic Sometimes you need to update a bunch of files in a directory at once, say you need to rewrite urls form one host to another on your website. share|improve this answer answered Jun 27 '12 at 17:37 Lars Kotthoff 72.4k9100117 add a comment| up vote 20 down vote More concisely: ! Bash Script Set E Beware that set -e doesn't always kick in.

When writing a wrapper script, you may wish pass along all the arguments your script received. exit $?

#!/bin/bash COMMAND1 . . . It's easy to forget this in normal, day-to-day development, and have it slip through the cracks. The wait builtin will return the exit code of the inner command, and now you're using || after wait, not the inner function, so set -e works properly inside the latter:

First, you can examine the contents of the $? Bash Script Set Variable From Command Output It will immediately stop your script if a simple command fails. true echo "exit status of \"! Consider this script named sayhello.sh: If you run "sayhello.sh" by itself, here's what happens: % ./sayhello.sh ./sayhello.sh: line 3: $1: unbound variable A most unhelpful error message.

Bash Script Set Environment Variable

I just wanted to add set -e as a rudimentary error mechanism. It's not, if nothing goes wrong. Bash Script Set Variable Allen Oct 22 '13 at 13:38 I was actually trying to check if a certain directory existed, not necessarily cd to it. Bash Script Set Password Conclusion When possible, instead of writing a "safe" shell script, use a higher-level language like Python.

Here $bar is set to "beta": bar=${foo:-alpha} # To make the default an empty string, use ${VARNAME:-} empty_string=${some_undefined_var:-} Under strict mode, you need to use this for all positional parameter references: http://onlinetvsoftware.net/bash-script/bash-script-bus-error.php Be prepared for spaces in filenames Someone will always use spaces in filenames or command line arguments and you should keep this in mind when writing shell scripts. 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. bash shell shell-script error-handling share|improve this question edited Oct 22 '13 at 22:58 Gilles 369k666681119 asked Oct 22 '13 at 10:29 Thomas De Wilde 28114 Just an FYI, you Bash Script Set Environment Variable For One Command

If you add a -p option then mkdir will create all the parent directories before creating the requested directory. The simplest, which you will usually want to use, is to append "|| true" after the command: # "grep -c" reports the number of matching lines. Skeletal formula for carbon with two double bonds Symbolic comparison of recursive functions Why did companions have such high social standing? his comment is here last_call=$1 # 127 is 'command not found' (( status != 127 )) && return echo "you tried to call $last_call" return } # Trap errors.

Commands in subshell only lead to exiting the subshell, not the parent: set -e; (false); echo foo displays foo. Bash Script Set Path Advanced Bash-Scripting Guide: PrevNext

Chapter 6. For the second loop, "words" are separated by a newline, which means bash considers the whole value of "items" as a single word.

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

Being intolerant of errors is a lot better in scripts, and that's what set -e gives you. What to tell to a rejected candidate? Reach me (Aaron Maxwell) by email, at amax at redsymbol dot net. Bash Script Set Working Directory replace all local x=y with just x=y: # [CLEANUP=cleanup_cmd] run cmd [args...] # # `cmd` and `args...` A command to run and its arguments. # # `cleanup_cmd` A command that is

Aaron Maxwell Wayne Gretzky David Beckham Anderson da Silva With strict-mode IFS value... echo $? # Non-zero exit status returned -- command failed to execute. For example, consider the following: [email protected] tmp [15:23] $ dir="foo bar" [email protected] tmp [15:23] $ ls $dir ls: cannot access foo: No such file or directory ls: cannot access bar: No http://onlinetvsoftware.net/bash-script/bash-script-error-127.php In strict mode, # next line triggers an error.

After a function returns, $? gives the exit status of the last command executed in the function. This very often produces useful splitting behavior. An advantage is that you now have a backup before you made your changes in case you need to revert. © 2013 Company Name current community chat Stack Overflow Meta Stack You then need to use -0 with xargs.

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. The second use, ${1:-"Unknown Error"} means that if parameter 1 ($1) is undefined, substitute the string "Unknown Error" in its place. In this case, the best choice is to use a block - i.e., curly braces: first_task && { second_task third_task } next_task Because we are using the -e option, if second_task