Bash Shell Script Error Logging
Contents |
am a new Ubuntu Linux and bash shell user. I also know how to redirect output from display/screen to a file using the following syntax:
cmd > file ls > fileHowever, some time errors are displayed on screen. How do I store bash shell script exit on error and redirect output from the computer screen to a file on a Linux or Unix-likeLinux Shell Script Logging
systems? Bash / ksh and other modern shell on Linux has three file descriptors:stdin (0)stdout (1)stderr (2)Syntax To redirect all output to fileThe linux log errors to file syntax is as follows to redirect output (stdout) as follows:command-name > output.txt command-name > stdout.txtSyntax To redirect all error to fileThe syntax is as follows to redirect errors (stderr) as follows:command-name 2> errors.txt command-name 2> stderr.txtSyntax to redirect
How To Check Error Logs In Linux
both output (stdout) and errors (stderr) to different filesThe syntax:command1 > out.txt 2> err.txt command2 -f -z -y > out.txt 2> err.txtSyntax to redirect both output (stdout) and errors (stderr) to same fileThe syntax is:command1 > everything.txt 2>&1 command1 -arg > everything.txt 2>&1Syntax to redirect errors (stderr) to null or zero devicesData written to a null or zero special file is discarded by your system. This is useful to silence out errors (also know as ‘error command required to redirect the standard error descriptor to a file in unix spam'):command1 2> /dev/null command1 2> /dev/zero command2 -arg 2> /dev/null command2 -arg 2> /dev/zeroTip: Use tee command to redirect to both a file and the screen same timeThe syntax is:command1 |& tee log.txt ## or ## command1 -arg |& tee log.txt ## or ## command1 2>&1 | tee log.txtAnother usage:#!/bin/bash # My script to do blah ... foo(){ : } 2>&1 | tee foo.logOR#!/bin/bash # My script to do blah ... { command1 command2 } 2>&1 | tee script.log Share this tutorial 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:BASH Shell Redirect Output and Errors To /dev/nullBASH Shell: How To Redirect stderr To stdout ( redirect stderr to a File )Unix and Linux: Redirect Error Output To null CommandHow do I save or redirect stdout and stderr into different files?Linux / Unix Find Command: Avoid Permission Denied MessagesShell Script While Loop ExamplesPrinting output of c program to a file in LinuxUnix / Linux: Save Output To FileLinux iptables: Port Redirection ExampleApplescript: Run or Call a Shell Script{ 10 comments… add one } Andrey Oliveira June 23, 2014, 12:15 pmIn newer versions of bash and sh, for "Syntax to redirect both output (stdout) and errors (stderr) to same file" y
could put at the top of your bash script: exec 1> >(logger -s -t $(basename $0)) 2>&1— Eric Lindvall (@lindvall) September 8, 2014 I could see roughly what was going on here, but I didn’t quite understand how it
Linux Redirect Stderr To File
worked. In particular, what on earth was the 1> >(logger ...) bit all about?
WhatLinux Redirect Stderr And Stdout To File
does it do? Adding this line to the top of your bash script will cause anything printed on stdout and stderr to linux output redirection 2 &1 be sent to the syslog1, as well as being echoed back to the original shell’s stderr. It’s certainly desirable to have your script output sent to a predictable location, so how does this work? Deconstructing the command The http://www.cyberciti.biz/faq/linux-redirect-error-output-to-file/ whole line again: exec 1> >(logger -s -t $(basename $0)) 2>&1 exec is a bash builtin, so to see what it does, we run help exec: exec: exec [-cl] [-a name] [command [args ...]] [redirection ...] Replace the shell with the given command. Execute COMMAND, replacing this shell with the specified program. ARGUMENTS become the arguments to COMMAND. If COMMAND is not specified, any redirections take effect in the current shell. In this case exec is http://urbanautomaton.com/blog/2014/09/09/redirecting-bash-script-output-to-syslog/ being used without COMMAND – this line is redirecting I/O for the current shell. So what do the redirections do? To simplify things let’s clear out the nested commands and just look at the redirection: exec 1> >(some-command) 2>&1 This is pretty simple redirection, obscured by that charming and easily google-able bash syntax that we all know and love bluff and tolerate. There are two redirections, the first being: 1> >(some-command) This redirects file descriptor 1 (stdout) to the location >(some-command). That’s not a normal filename, though: it’s a process substitution, which is a non-POSIX bash feature2. >(some-command) returns a file descriptor that some-command will use as its stdin. This is exactly the same as piping our script’s stdout into some-command. Then we redirect file descriptor 2 (stderr) to the same location as file descriptor 1: 2>&1 In summary, we’ve redirected both stdout and stderr for our script to the same place: the stdin for another process, which is a command running in the background. In effect, this is the same as running the script at the command line like so: $ ./some-script 2>&1 | some-command In this case, some-command is: logger -s -t $(basename $0) From the logger(1) manpage we can see that this writes entries to syslog, tagged (-t) with the filename of our script ($(basename $0)) and echoing them to standard
Start here for a quick overview of the site Help Center Detailed answers to any questions you might have Meta Discuss the workings and policies http://serverfault.com/questions/103501/how-can-i-fully-log-all-bash-scripts-actions of this site About Us Learn more about Stack Overflow the company Business Learn more about hiring developers or posting ads with us Server Fault Questions Tags Users Badges Unanswered Ask Question _ Server Fault is a question and answer site for system and network administrators. Join them; it only takes a minute: Sign up Here's how it works: Anybody can ask a question shell script Anybody can answer The best answers are voted up and rise to the top How can i fully log all bash scripts actions? up vote 18 down vote favorite 19 I want to capture ALL the logs data, both with error messages, from my script output, and redirect them all to log file. I have script like below: #!/bin/bash ( echo " `date` bash shell script : part 1 - start " ssh -f admin@server.com 'bash /www/htdocs/server.com/scripts/part1.sh logout exit' echo " `date` : sleep 120" sleep 120 echo " `date` : part 2 - start" ssh admin@server.com 'bash /www/htdocs/server.com/scripts/part2.sh logout exit' echo " `date` : part 3 - start" ssh admin@server.com 'bash /www/htdocs/server.com/scripts/part3.sh logout exit' echo " `date` : END" ) | tee -a /home/scripts/cron/logs I want to see all actions in file "/home/scripts/cron/logs" But i see only this what i put after echo command. How to check in logs is SSH command was successful? I need to gather all the logs data. I need this to monitor result of every command in my script, to better analyse what's going on while script fail. linux ssh bash scripting log-files share|improve this question edited Sep 6 '13 at 18:57 asked Jan 17 '10 at 11:17 BlueMark 209127 You can also use the "script" to perform this. See this post: [here][1] [1]: stackoverflow.com/questions/5985060/… –xX0v0Xx Jun 3 '14 at 12:57 you must be careful with errexit - I noticed it is ignored or error does not exit script eg. if you have something like