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Bash Script Return Error

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Note the inclusion # of the LINENO environment variable. construct is generally better expressed as if cmd; then ... Especially if that script is used for the command line. true !true # No error this time, but no negation either. # It just repeats the previous command (true). # =========================================================== # # Preceding a _pipe_ with ! this contact form

The benefit of using -e is that it prevents errors snowballing into serious issues when they could have been caught earlier. Browse other questions tagged bash . The lockfile will be left there and your script won't run again until it's been deleted. You could fix this using a backup and a trap, but you also have the problem that the site will be inconsistent during the upgrade too.

Bash Script Return Error Message

A careful reading of the output of help set shows: -e Exit immediately if a command exits with a non-zero status. Please recheck the variables 1>&2 exit 1 # terminate and indicate error fi ... That implies that the user of the script is also the developer. –Alex Jul 25 at 12:05 add a comment| up vote 24 down vote If you want to be able The solution to this is to make the changes an (almost) atomic operation.

Race conditions It's worth pointing out that there is a slight race condition in the above lock example between the time we test for the lockfile and the time we create You can surround a variable name with curly braces (as with ${PROGNAME}) if you need to be sure it is separated from surrounding text. 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 Script Return Exit Code The next approach we can try is to use the if statement directly, since it evaluates the exit status of commands it is given.

The Woz Monitor What does the "Phi" sign stand for in musical notation? Exit Bash Script Early echo "Example of error with line number and message" error_exit "$LINENO: An error has occurred." The use of the curly braces within the error_exit function is an example of parameter expansion. To my surprise, I can't achieve this. (set -e is not enough.) Example: #!/bin/bash # Do exit on any error: set -e readonly a=(1 2) # A syntax error is here: The second use, ${1:-"Unknown Error"} means that if parameter 1 ($1) is undefined, substitute the string "Unknown Error" in its place.

share|improve this answer answered Dec 8 '10 at 5:12 Dennis Williamson 167k42235305 add a comment| up vote 2 down vote Here is the way to do it: #!/bin/sh abort() { echo Bash Script Return Value From Command Convince people not to share their password with trusted others Meaning of Guns and ghee Skeletal formula for carbon with two double bonds Is 8:00 AM an unreasonable time to meet GTIN validation How would family relationships change if legal system uses collective punishment? Exit and Exit Status...

  • Unfortunately shell scripts are full of subtle effects which result in scripts failing in unusual ways.
  • asked 4 years ago viewed 3478 times active 4 years ago Linked 5 How to make bash alias invocation conditional on PWD?
  • So, all you really need is: #!/usr/bin/env bash install_auto() { apt-get -h > /dev/null 2>&1 if [ $? -eq 0 ] ; then sudo apt-get install --assume-yes $@ fi } You

Exit Bash Script Early

When taking passengers, what should I do to prepare them? so you want: if [ ${#a[*]} -eq 2 ]; then share|improve this answer edited Jul 8 '13 at 19:16 Evan Teitelman 13.1k43758 answered Jul 8 '13 at 17:18 higuita 47237 Bash Script Return Error Message You then need to use -0 with xargs. Bash Script Return Value if the "then" part is just a simple command. –tripleee Jul 8 '13 at 6:00 add a comment| Your Answer draft saved draft discarded Sign up or log in Sign

It would be nice if you could fix these problems, either by deleting the lock files or by rolling back to a known good state when your script suffers a problem. weblink But I find it still unreasonable to continue executing afte a syntax error. Another example is rm. This can be fixed by using: if [ "$filename" = "foo" ]; When using $@ variable, you should always quote it or any arguments containing a space will be expanded in Bash Script Carriage Return

It is also important that your scripts return a meaningful exit status when they finish. You can also reset traps back to their default by using - as the command.   Signal Description INT Interrupt - This signal is sent when someone kills the script by pressing ctrl-c. Join them; it only takes a minute: Sign up Here's how it works: Anybody can ask a question Anybody can answer The best answers are voted up and rise to the navigate here Were slings used for throwing hand grenades?

An OR list has the form command1 || command2 command2 is executed if, and only if, command1 returns a non-zero exit status. Bash Script Return True If the touch command fails however, we will print a failure message to stderr and exit with a 1 value which indicates failure. You can see this work with the following: [me] $ true; echo $? 0 [me] $ false; echo $? 1 The true and false commands are programs that do nothing except

might be sufficient.

Browse other questions tagged bash exit shell or ask your own question. 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 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 Bash Script Return From Function Unfortunately it means you can't check $?

To do this make a copy of the data, make the changes in the copy, move the original out of the way and then move the copy back into place. You can read more about parameter expansion in the bash man page under the topic "EXPANSIONS". I want it to store inside a string first so I can format the contents easily. –Miguel Roque May 29 '14 at 7:45 1 @MiguelRoque see updates –Networker May 29 http://waspsoft.com/bash-script/bash-script-error.html after every statement to catch syntax errors. (I expected such safe behavior from a sensible programming language...