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the == will also work, but -eq is recommended. If the exit status is anything other than zero, then the program failed in some way. Program defensively - expect the unexpected Your script should take into account of the unexpected, like files missing or directories not being created. Join them; it only takes a minute: Sign up Exit a Script On Error up vote 43 down vote favorite 7 I'm building a Shell Script that has a if function

there are dark corners in the Bourne shell, and people use all of them.

--Chet Ramey

The exit command terminates a script, Players stopping other player actions Is there a place in academia for someone who compulsively solves every problem on their own? I've appended echo 'Bad2: has not aborted the execution after bad main!' as the last to your example, and the output is: $ LC_ALL=C ./sh-on-syntax-err ./sh-on-syntax-err: line 6: #: syntax error: Thread Tools Show Printable Version Subscribe to this Thread… Display Linear Mode Switch to Hybrid Mode Switch to Threaded Mode December 11th, 2008 #1 jasper.davidson View Profile View Forum Posts Private

In general, it is considered bad practice to use set -e, because all errors (i.e., all non-zero returns from commands) should be smartly handled by the script (think robust script, not How to get this substring on bash script? It's possible to write scripts which minimise these problems. Related 2123Check if a directory exists in a shell script2913Can a Bash script tell which directory it is stored in?241Exit Shell Script Based on Process Exit Code726How do I prompt for

Thanks again. 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 The problem with the script was that it did not check the exit status of the cd command before proceeding with the rm command. so you want: if [ ${#a[*]} -eq 2 ]; then share|improve this answer edited Jul 8 '13 at 19:16 Evan Teitelman 13.3k43758 answered Jul 8 '13 at 17:18 higuita 47237

Chapter 33. For details and our forum data attribution, retention and privacy policy, see here current community chat Unix & Linux Unix & Linux Meta your communities Sign up or log in Maybe some Bash gurus will join in and clarify everything. Bash One Liner: $ ./tmp.sh && echo "bam" || (sudo ./tmp.sh && echo "bam" || echo "fail") Could not create file Successfully created file bam The above grouping of commands use

No, (( )) makes no difference! This is the best bash guide around. On top of those reasons, exit codes exist within your scripts even if you don't define them. exit / exit status

#!/bin/bash echo hello echo $? # Exit status 0 returned because command executed successfully.

First, you can examine the contents of the $? david% bash /tmp/shrink-chroot.sh $chroot= david% bash -u /tmp/shrink-chroot.sh /tmp/shrink-chroot.sh: line 3: $1: unbound variable david% Use set -e Every script you write should include set -e at the top. Sample Script: #!/bin/bash touch /root/test echo created file The above sample script will execute both the touch command and the echo command. up vote 14 down vote favorite 5 To be on safe side, I'd like bash abort the execution of a script if it encounters a syntax error.

The Linux Documentation Project has a pretty good table of reserved exit codes and what they are used for. To help explain exit codes a little better we are going to use a quick sample script. PROGNAME=$(basename $0) function error_exit { # ---------------------------------------------------------------- # Function for exit due to fatal program error # Accepts 1 argument: # string containing descriptive error message # ---------------------------------------------------------------- echo "${PROGNAME}: ${1:-"Unknown If you use find and xargs together, you should use -print0 to separate filenames with a null character rather than new lines.

Within a script, an exit nnn command may be used to deliver an nnn exit status to the shell (nnn must Buy on Amazon Sponsored by Become a Sponsor Copyright © Benjamin Cane 2014 - Contact the Author Adv Reply December 11th, 2008 #4 jasper.davidson View Profile View Forum Posts Private Message 5 Cups of Ubuntu Join Date Jul 2008 Beans 26 Re: Make shell script exit as You need to make sure that both the old and the new directories are moved to locations that are on the same partition so you can take advantage of the property

Is there possibly some way around that? rm -rf $chroot/usr/share/doc If you ran the script above and accidentally forgot to give a parameter, you would have just deleted all of your system documentation rather than making a smaller Or you could do something cheesy like: Code: #!/bin/bash function execCmd() { eval "$1" status=$? More exit codes The exit command in bash accepts integers from 0 - 255, in most cases 0 and 1 will suffice however there are other reserved exit codes that can

This site is not affiliated with Linus Torvalds or The Open Group in any way. Especially if that script is used for the command line. You can read more about parameter expansion in the bash man page under the topic "EXPANSIONS". Browse other questions tagged bash exit shell or ask your own question.

Also the time where it is affected is reduced to the time between the two mvs, which should be very minimal, as the filesystem just has to change two entries in the Is there a place in academia for someone who compulsively solves every problem on their own? The lockfile will be left there and your script won't run again until it's been deleted. Is there any job that can't be automated?

share|improve this answer answered May 20 '10 at 4:34 sth 127k33204308 More information here: davidpashley.com/articles/… –dhornbein Jun 13 '13 at 3:39 add a comment| up vote 28 down vote the # doesn't have any array meaning I don't know what you want to do with this, but I assume you want to know the number of fields, so you want Using exit codes in your bash scripts While removing the echo command from our sample script worked to provide an exit code, what happens when we want to perform one action vBulletin 2000 - 2016, Jelsoft Enterprises Ltd.

In that case, the cd command will fail and the script executes the rm command on the current working directory. Is the NHS wrong about passwords? Why is it a bad idea for management to have constant access to every employee's inbox How do you say "root beer"? 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";

The above command will execute the ./tmp.sh script, and if the exit code is 0 the command echo "bam" will be executed. The second use, ${1:-"Unknown Error"} means that if parameter 1 ($1) is undefined, substitute the string "Unknown Error" in its place. In other words, there are just a few commands in my script that it doesn't matter if they return an error, and I don't want the entire script to terminate for That's the intended behavior.

Why would a password requirement prohibit a number in the last character? That usage is simply a style thing. In that case, the shell will interpret the variable as empty and the cd succeed, but it will change directories to the user's home directory, so beware!