Bash Last Error Message
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Bash Display Error Message
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Bash Exit With Error Message
can answer The best answers are voted up and rise to the top Is it possible to get the error message from previous command which failed when the conditional command runs using || up vote 5 down vote favorite 2 I have a helper function: function error_exit { /opt/aws/bin/cfn-signal ... exit 1 } This helper function is used to signal an error. Here is an example of usage: /opt/aws/bin/cfn-init -s
Bash Print Error Message
.. || error_exit 'Failed to run cfn-init' The cfn-init command takes a lot of parameters which isn't relevant for the question. When the command returns a non-null value and possibly an error message to the error output, I would like to get the error message and include it to the error_exit method as a parameter. Is this possible? If not, how would you implement a helper method in bash which makes it possible to get the source error message? bash shell error-handling share|improve this question edited Dec 20 '11 at 23:31 Gilles 369k666681119 asked Dec 20 '11 at 11:00 tronda 182111 In the context of CloudFormation's stock templates, from which this looks to derive, also consider setting 'DisableRollback' with --disable-rollback in the CLI tools. Also use cfn-init's -v flag to get verbose output. –Christopher Jul 23 '12 at 13:22 add a comment| 2 Answers 2 active oldest votes up vote 6 down vote accepted You can redirect the error output to a file and then retrieve that output: trap "rm -f /tmp/cfn-error.txt" 0 1 2 3 15 /opt/aws/bin/cfn-init -s ... 2>/tmp/cfn-error.txt || error_exit $(
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Bash Return Last Error Code
OMG! Ubuntu Ubuntu Insights Planet Ubuntu Activity Page Please read before SSO login Advanced Search Forum The Ubuntu Forum Community Ubuntu Specialised bash throw error Support Development & Programming Programming Talk [SOLVED] Bash error message handling Having an Issue With Posting ? Do you want to help us debug the posting issues ? < is the place to report it, thanks http://unix.stackexchange.com/questions/27218/is-it-possible-to-get-the-error-message-from-previous-command-which-failed-when ! Results 1 to 6 of 6 Thread: [SOLVED] Bash error message handling Thread Tools Show Printable Version Subscribe to this Thread… Display Linear Mode Switch to Hybrid Mode Switch to Threaded Mode February 6th, 2008 #1 roggo View Profile View Forum Posts Private Message Spilled the Beans Join Date Oct 2007 Beans 14 DistroUbuntu 7.10 Gutsy Gibbon [SOLVED] Bash error message handling Hello all! I have a simple question, and my https://ubuntuforums.org/showthread.php?t=689289 searches have not found an answer so I want your help! How do I find the string of the error message of a command? In example... ls "this file does not exist.txt" echo THE_ERROR_FROM_LS # (no such file or dir) Thanks! Adv Reply February 6th, 2008 #2 ghostdog74 View Profile View Forum Posts Private Message I Ubuntu, Therefore, I Am Join Date Sep 2006 Beans 2,914 Re: Bash error message handling Originally Posted by roggo Hello all! I have a simple question, and my searches have not found an answer so I want your help! How do I find the string of the error message of a command? In example... ls "this file does not exist.txt" echo THE_ERROR_FROM_LS # (no such file or dir) Thanks! echo $? that's the return status. is that what you want. Also, pls try to read the bash manual next time. Python tutorial |Unix power tools|Effective AWK|A handful of Awk|Perl|File Renamer|Bash ref Adv Reply February 6th, 2008 #3 roggo View Profile View Forum Posts Private Message Spilled the Beans Join Date Oct 2007 Beans 14 DistroUbuntu 7.10 Gutsy Gibbon Re: Bash error message handling Originally Posted by ghostdog74 echo $? that's the return status. is that what you want. Also, pls try to read the bash manual next ti
here for a quick overview of the site Help Center Detailed answers to any questions you might have Meta Discuss the workings and policies of this site http://stackoverflow.com/questions/12966622/make-bash-script-exit-and-print-error-message-if-users-invoke-the-script-incorre About Us Learn more about Stack Overflow the company Business Learn more about hiring developers or posting ads with us Stack Overflow Questions Jobs Documentation Tags Users Badges Ask Question x Dismiss http://www.cyberciti.biz/tips/shell-displaying-error-messages.html Join the Stack Overflow Community Stack Overflow is a community of 4.7 million programmers, just like you, helping each other. Join them; it only takes a minute: Sign up Make Bash script error message exit and print error message if users invoke the script incorrectly up vote 3 down vote favorite 1 Script needed was #!/bin/bash # Check if there are two arguments if [ $# -eq 2 ]; then # Check if the input file actually exists. if ! [[ -f "$1" ]]; then echo "The input file $1 does not exist." exit 1 fi else echo "Usage: bash last error $0 [inputfile] [outputfile]" exit 1 fi # Run the command on the input file grep -P "^[\s]*[0-9A-Za-z-]+.?[\s]*$" "$1" > "$2" Edit, the script has changed to grep -P "^[\s]*[0-9A-Za-z-]+.?[\s]*$" $* if [ ! -f "$1" ]; then echo 'Usage: ' echo echo './Scriptname inputfile > outputfile' exit 0 fi invoking the script with no parameters gives no erros and sits blank Usage: ./Scriptname inputfile > outputfile I have bit of code grep -P "^[\s]*[0-9A-Za-z-]+.?[\s]*$" $* This code pulls lines that have a single word on them and pumps the output to a new file, so for example This is a multi word line this the above line is not now once again wrong The output would be This now The code works, users invoke the code using ./scriptname file > newfile However, I am trying to expand the code to give users an error message if they invoke the script incorrectly. For the error messange, I'm thinking of echoing something back like scriptname file_to_process > output_file. I did try if [incorrectly invoted unsure what to type] echo $usage exit 1 Usage="usage [inputfile] [>] [outputfile] However I have had little luck. The code
March 20, 2016 in Debian Linux, FreeBSD, Linux, OpenBSD, RedHat/Fedora Linux, Shell scripting, Suse Linux, Ubuntu Linux, UNIXWhile writing a shell script you may need to display an error message. For example, if you failed to open /etc/passwd file you want to show an error message.
The old methodYou can write something as follows on bash using the if statement to test a conditioncat /etc/shadow 2>/dev/null if [ $? -ne 0 ]; then echo "Failed to open file"; exit 1 ; fiThe new way: OR || control operatorHowever, you can use the control operator || (or lists). It has the form as follows: command1 || command2 command2 is executed if and only if command1 returns a non-zero exit status. For example: $ cat /etc/shadow 2>/dev/null || echo "Failed to open file" This way you display an error message. Another option is to create die shell function:#!/bin/bash function die(){ echo "$1" exit 1 } # ... # ... other code cat /etc/shadow 2>/dev/null || die "Failed to open file" # rest of my scriptAND (&&) control operatorSimilarly you can use AND (&&) control operator. It has the form/syntax: command1 && command2 The command2 is executed if, and only if, command1 returns an exit status of zero. For example: $ cat /etc/shadow 2>/dev/null && echo "I can open /etc/shadow file." You can combine both to produce useful message in a script:#!/bin/bash ... tar -zcf /dev/st0 /data2 && echo "/data2/ added to backup device" || echo "Warning: Cannot add /data2/ to backup device." .... Share this on:TwitterFacebookGoogle+Download PDF version Found an error/typo on this page?About the author: Vivek Gite is a seasoned sysadmin and a trainer for the Linux/Unix & shell scripting. Follow him on Twitter. OR read more like this:How do I find the exit status of a remote command executed via ssh?BASH Shell: How to run several commands in Sequence or all at onceHowTo: Debug a Shell Script Under Linux or UNIXBash shell script tip: Run commands from a variableTest your Samba server for configuration errorsLinux / UNIX: Find Out If a Directory Exists or NotTake action or execute a command based upon shell script nameLinux/UNIX: Find Out If File Exists With Conditional ExpressionsDebian / Ubuntu Package Troubleshooting: subprocess post-removal script…Increase productivity with FTP autologin and macros{ 0 comments… add one } Sec