Capture Standard Error
Contents |
12, 2008 in BASH Shell, Linux, UNIXQ. How do I redirect stderr to stdout? How do I redirect stderr to a file? A. Bash and other modern shell provides I/O redirection facility. There standard output and standard error to file are 3 default standard files (standard streams) open: [a] stdin - Use to get
Bash Redirect Output And Error
input (keyboard) i.e. data going into a program.
[b] stdout - Use to write information (screen)[c] stderr - Use to write shell standard output error message (screen)Understanding I/O streams numbersThe Unix / Linux standard I/O streams with numbers:HandleNameDescription0 stdin Standard input1 stdout Standard output2 stderr Standard errorRedirecting the standard error stream to a fileThe following will redirect program errorCombine Stderr And Stdout
message to a file called error.log: $ program-name 2> error.log
$ command1 2> error.logRedirecting the standard error (stderr) and stdout to fileUse the following syntax: $ command-name &>file OR $ command > file-name 2>&1 Another useful example: # find /usr/home -name .profile 2>&1 | moreRedirect stderr to stdoutUse the command as follows: $ command-name 2>&1 Share this tutorial on:TwitterFacebookGoogle+Download PDF version Found an error/typo on this page?About the redirect standard error and output to different files 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 save or redirect stdout and stderr into different files?Linux Redirect Error Output To FileBASH Shell Redirect Output and Errors To /dev/nullUnix and Linux: Redirect Error Output To null CommandPrinting output of c program to a file in LinuxUnix / Linux: Save Output To FilePython Run External Command And Get Output On Screen or In VariablePython Execute Unix / Linux Command ExamplesLinux / Unix Find Command: Avoid Permission Denied MessagesHow to gzip and keep original file on Unix or Linux command line{ 11 comments… add one } Sayed Ahmad February 12, 2012, 12:11 amWhat this mean? $ command > file-name 2>&1 Reply Link Hesham M January 22, 2014, 3:34 pmThis means redirect stdout to file-name, with that in mind redirect stderr t stdout. This will lead to both stderr and stdout go to file-name. Reply Link Shane Hathaway February 24, 2012, 1:02 amSayed: that line means execute the command while redirecting both stdout and stderr to a file given by file-name. Reply Link RudyD April 2, 2012, 12:47 pmGreetings! A slightly more correct is: The output of the ‘command' is redirecte
>20.3. Applications
Redirect Standard Error And Output To /dev/null
(error messages output to the screen). These, and any other open
Redirect Standard Error And Standard Out To File
files, can be redirected. Redirection simply means capturing output from a file, command, program, script, or even code redirect standard error and output to file windows block within a script (see Example 3-1 and Example 3-2) and sending it as input to another file, command, program, or script.
Each open file gets assigned http://www.cyberciti.biz/faq/redirecting-stderr-to-stdout/ a file descriptor. [2] The file descriptors for stdin, stdout, and stderr are 0, 1, and 2, respectively. For opening additional files, there remain descriptors 3 to 9. It is sometimes useful to assign one of these additional file descriptors to stdin, stdout, or stderr as a temporary duplicate link. [3]http://www.tldp.org/LDP/abs/html/io-redirection.html > This simplifies restoration to normal after complex redirection and reshuffling (see Example 20-1). COMMAND_OUTPUT > # Redirect stdout to a file. # Creates the file if not present, otherwise overwrites it. ls -lR > dir-tree.list # Creates a file containing a listing of the directory tree. : > filename # The > truncates file "filename" to zero length. # If file not present, creates zero-length file (same effect as 'touch'). # The : serves as a dummy placeholder, producing no output. > filename # The > truncates file "filename" to zero length. # If file not present, creates zero-length file (same effect as 'touch'). # (Same result as ": >", above, but this does not work with some shells.) COMMAND_OUTPUT >> # Redirect stdout to a file. # Creates the file if not present, otherwise appends to it. # Single-line redirection commands (affect only the line they are on): # -------------------------------------------------------------------- 1>filename # Redirect stdout to file "filename." 1>>filename # Redirect and append stdout to file "filename." 2>filename # Redirect stderr tohere 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 About Us Learn more about Stack Overflow the company Business Learn more about hiring developers or http://stackoverflow.com/questions/11087499/bash-how-do-you-capture-stderr-to-a-variable posting ads with us Stack Overflow Questions Jobs Documentation Tags Users Badges Ask Question x Dismiss 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 http://www.perlmonks.org/?node=How%20can%20I%20capture%20STDERR%20from%20an%20external%20command%3F a minute: Sign up Bash how do you capture stderr to a variable? [duplicate] up vote 15 down vote favorite 5 This question already has an answer here: Bash script - store stderr in variable [duplicate] 4 answers Bash how standard error do you capture stderr to a variable? I would like to do something like this inside of my bash script sh -c path/myExcecutable-bin 2>&1 =MYVARIABLE How do you send stderror output to a variable ? bash stderr share|improve this question edited Jun 18 '12 at 16:57 Tim Pote 13.4k23344 asked Jun 18 '12 at 16:55 stackoverflow 4,0212380143 marked as duplicate by tripleeebash Users with the bash badge can single-handedly close bash questions as duplicates and reopen them as needed. Mar 14 redirect standard error at 6:56 This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question. 2 This StackOverflow thread should answer your question. –Web User Jun 18 '12 at 16:57 See one of the many related threads, and several solutions –ormaaj Jun 18 '12 at 17:01 add a comment| 1 Answer 1 active oldest votes up vote 33 down vote accepted To save both stdin and stderr to a variable: MYVARIABLE="$(path/myExcecutable-bin 2>&1)" To save just stderr to a variable: MYVARIABLE="$(path/myExcecutable-bin 2>&1 > /dev/null)" share|improve this answer edited Jun 18 '12 at 17:06 answered Jun 18 '12 at 16:56 Tim Pote 13.4k23344 4 I just want to note that you will save both stderr and stdout to the variable. When you need only stderr use 2>&1 >/dev/null –Igor Chubin Jun 18 '12 at 16:59 @IgorChubin Good point. I was basing my original answer on what it looked like the OP wanted to do, but that isn't necessarily what they actually wanted. See my changes. –Tim Pote Jun 18 '12 at 17:08 add a comment| Not the answer you're looking for? Browse other questions tagged bash stderr or ask your own question. asked 4 years ago viewed 15244 times active 7 months ago Linked 28 Bash script - store stderr in variable 1 Output of a command not passing to assigned variable 88 How to st
CoolUsesForPerl PerlNews Q&A Tutorials Poetry RecentThreads NewestNodes Donate What'sNew on Oct 08, 1999 at 00:29UTC ( #730=perlfaq nodetype: print w/replies, xml ) Need Help?? Current Perl documentation can be found at perldoc.perl.org. Here is our local, out-dated (pre-5.6) version: There are three basic ways of running external commands: system $cmd; # using system() $output = `$cmd`; # using backticks (``) open (PIPE, "cmd |"); # using open() With system(), both STDOUT and STDERR will go the same place as the script's versions of these, unless the command redirects them. Backticks and open() read only the STDOUT of your command. With any of these, you can change file descriptors before the call: open(STDOUT, ">logfile"); system("ls"); or you can use Bourne shell file-descriptor redirection: $output = `$cmd 2>some_file`; open (PIPE, "cmd 2>some_file |"); You can also use file-descriptor redirection to make STDERR a duplicate of STDOUT: $output = `$cmd 2>&1`; open (PIPE, "cmd 2>&1 |"); Note that you cannot simply open STDERR to be a dup of STDOUT in your Perl program and avoid calling the shell to do the redirection. This doesn't work: open(STDERR, ">&STDOUT"); $alloutput = `cmd args`; # stderr still escapes This fails because the open() makes STDERR go to where STDOUT was going at the time of the open(). The backticks then make STDOUT go to a string, but don't change STDERR (which still goes to the old STDOUT). Note that you must use Bourne shell (sh(1)) redirection syntax in backticks, not csh(1)! Details on why Perl's system() and backtick and pipe opens all use the Bourne shell are in http://www.perl.com/CPAN/doc/FMTEYEWTK/versus/csh.whynot . To capture a command's STDERR and STDOUT together: $output = `cmd 2>&1`; # either with backticks $pid = open(PH, "cmd 2>&1 |"); # or with an open pipe while (