The problem with the script was that it did not check the exit status of the cd command before proceeding with the rm command. Any script that is useful in some fashion will inevitably be either used in another script, or wrapped with a bash one liner. anny >Real ProgrammersMost programmers will prefer to use the test built-in command, which is equivalent to using If the first fails, then valid_ip fails. http://silkiconfinder.com/exit-code/bash-echo-return-code.html
command ] doesn't execute command; it treats command as a string and treats it as true because it has a non-zero length. [ is a synonym for the test command –Keith A Little Cryptic Puzzle Why are copper cables round? Why are Zygote and Whatsapp asking for root? Using them, we can see how the $?
I prefer Keith Thompson's answer. –janmoesen Oct 17 '11 at 11:30 4 There are benefits to this idiom -- it preserves the return value. The return status is the exit status of the last command executed, or zero if no condition tested true.
Can anyone suggest what should I do here ? Execution: $ ./tmp.sh Could not create file $ echo $? 1 Using exit codes on the command line Now that our script is able to tell both users and programs whether Keeping windshield ice-free without heater Pi == 3.2 How to help reduce students' anxiety in an oral exam? http://bencane.com/2014/09/02/understanding-exit-codes-and-how-to-use-them-in-bash-scripts/ To explain how they work, I will quote from the bash man page: "The control operators && and || denote AND lists and OR lists, respectively.
if [ ! Bash Not Equal It is most often used if the input requested from the user is incorrect, if a statement did not run successfully or if some other error occurred.The exit statement Why leave magical runes exposed? Boolean operationsThe above script can be shortened using the Boolean operators "AND" (&&) and "OR" (||).Figure 7-2.
No need to store or return explicit return codes. Discover More Digital Hardness of Integers Should we kill the features that users are not using frequently, to improve performance? Shell Script Exit Code This is such a common pitfall that it has its own entry in BashPitfalls: mywiki.wooledge.org/BashPitfalls#cmd1_.26.26_cmd2_.7C.7C_cmd3 –Flimm Nov 10 '11 at 23:10 1 @Flimm: I don't agree it's a bad pattern. Bash Script Exit On Error Do they wish to personify BBC Worldwide?
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 weblink What am I doing wrong? First, you can examine the contents of the $? The most natural way to transpose this into code is something like: if [ ! Bash If Exit Code Not 0
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 A single word for "the space in between" Should I use the tax table or the tax rate schedule for calculating my tax? Where can I find Boeing 777 safety records? navigate here Anyway, a little testing should clear any ambiguities. –ata Nov 11 '11 at 0:26 add a comment| up vote -1 down vote this might help you , in bash [[email protected] ~]$
echo "exit status of \"true\" = $?" # 0 ! Exit Bash Shell special variable to print the exit code of the script. While this is a working solution to the problem, there are more clever methods that will save us some typing.
This value is referred to as an exit code or exit status. Why isn't the religion of R'hllor, The Lord of Light, dominant? share|improve this answer answered Jul 10 '13 at 14:30 choroba 111k1096155 Please take a look on my edit. –Patryk Jul 10 '13 at 15:12 @Patryk: Note that Exit Code 0 Below, a couple of simple examples.
Are you certain that echo will always return a 0 exit status? So it could be #!/bin/sh some command if [ $? == 0 ] echo '
So if [ ... ] is equivalent to if test ... –coldfix Aug 20 '13 at 4:32 add a comment| up vote 4 down vote You don't need the [ ]
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