Bash Filter Error Output
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Bash Error Output To Variable
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Bash Error Output To Dev/null
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Bash Redirect Error Output
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 top How to grep standard error stream (stderr)? up vote 48 down vote favorite 15 I am using ffmpeg to get the meta info of an audio clip. But I am unable to grep it. $ ffmpeg -i 01-Daemon.mp3 bash suppress error output |grep -i Duration FFmpeg version SVN-r15261, Copyright (c) 2000-2008 Fabrice Bellard, et al. configuration: --prefix=/usr --bindir=/usr/bin --datadir=/usr/share/ffmpeg --incdir=/usr/include/ffmpeg --libdir=/usr/lib --mandir=/usr/share/man --arch=i386 --extra-cflags=-O2 ... I checked, this ffmpeg output is directed to stderr. $ ffmpeg -i 01-Daemon.mp3 2> /dev/null So I think that grep is unable to read error stream to catch matching lines. How can we enable grep to read error stream? Using nixCraft link, I redirected standard error stream to standard output stream, then grep worked. $ ffmpeg -i 01-Daemon.mp3 2>&1 | grep -i Duration Duration: 01:15:12.33, start: 0.000000, bitrate: 64 kb/s But what if we do not want to redirect stderr to stdout? grep io-redirection ffmpeg share|improve this question edited Oct 31 '10 at 5:25 Stefan 8,3851966111 asked Oct 26 '10 at 1:42 Andrew-Dufresne 1,12831318 1 I believe that grep can only operate on stdout (Although I can't find the canonical source to back that up), which means that any stream needs to be converted to stdout first. –Stefan Lasiewski Oct 26 '10 at 18:20 6 @Stefan: grep can only operate on stdin. It's the pipe created by the shell that connects g
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 About Us Learn more about Stack Overflow the bash hide error output company Business Learn more about hiring developers or posting ads with us Stack Overflow Questions bash capture error output Jobs Documentation Tags Users Badges Ask Question x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 4.7 million bash script error output programmers, just like you, helping each other. Join them; it only takes a minute: Sign up bash command to grep something on stderr and save the result in a file up vote 5 down vote favorite http://unix.stackexchange.com/questions/3514/how-to-grep-standard-error-stream-stderr I am running a program called stm. I want to save only those stderr messages that contain the text "ERROR" in a text file. I also want the messages on the console. How do I do that in bash? bash shell share|improve this question edited May 1 '13 at 15:43 Joseph Quinsey 5,69592851 asked May 1 '13 at 15:41 user2339933 2814 add a comment| 3 Answers 3 active oldest votes up vote 8 down http://stackoverflow.com/questions/16321415/bash-command-to-grep-something-on-stderr-and-save-the-result-in-a-file vote accepted Use the following pipeline if only messages containing ERROR should be displayed on the console (stderr): stm |& grep ERROR | tee -a /path/to/logfile Use the following command if all messages should be displayed on the console (stderr): stm |& tee /dev/stderr | grep ERROR >> /path/to/logfile Edit: Versions without connecting standard output and standard error: stm 2> >( grep --line-buffered ERROR | tee -a /path/to/logfile >&2 ) stm 2> >( tee /dev/stderr | grep --line-buffered ERROR >> /path/to/logfile ) share|improve this answer edited May 2 '13 at 18:08 answered May 1 '13 at 15:43 nosid 28.6k35598 3 |& will connect both standard output and standard error to the RHS of the pipeline. –chepner May 1 '13 at 16:12 stm |& grep ERROR seems to filter out the messages containing ERROR to the console,but for some reason the teeing to the logfile always seems to return an empty file,Even if I dont want it on the console, stm|& grep ERROR > logfile.txt does'nt work. –user2339933 May 2 '13 at 8:26 add a comment| up vote 1 down vote This looks like a duplicate of How to pipe stderr, and not stdout? Redirect stderr to "&1", which means "the same place where stdout is going". Then redirect stdout to /dev/null. Then use a normal
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 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 http://askubuntu.com/questions/24953/using-grep-with-pipe-and-ampersand-to-filter-errors-from-find Learn more about hiring developers or posting ads with us Ask Ubuntu Questions Tags Users Badges http://xmodulo.com/how-to-suppress-warning-or-error-messages-in-find-command.html Unanswered Ask Question _ Ask Ubuntu is a question and answer site for Ubuntu users and developers. 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 top using grep with pipe and ampersand to filter errors from find up vote error output 12 down vote favorite I am using cygwin to find a file on the cygdrive. However I need to suppress the permission denied messages (otherwise the results get hidden in the error messages). The following command works: find -name 'myfile.*' |& grep -v "Permission denied" I don't understand why the ampersand needs to be put into this command, would have expected this to work but it doesn't. find -name 'myfile.*' | grep -v "Permission denied" Please explain bash error output the meaning of the ampersand. bash command-line find grep share|improve this question edited Feb 7 '11 at 6:33 Kees Cook 12.4k65085 asked Feb 5 '11 at 19:25 HKK 163115 add a comment| 3 Answers 3 active oldest votes up vote 13 down vote accepted In Unix-like systems, there are two output paths that if left unmodified will send output to your screen. Standard error (or stderr) is the one that captures most failures and error conditions. To pass the permission denied message in the stderr to the same output stream as "regular output" you must combine the two. In your example, in order for your grep -v to properly operate on it, you combine stdout (standard output) and stderr with the arcane syntax you see. From the advanced bash scripting guide : If ‘|&’ is used, the standard error of command1 is connected to command2's standard input through the pipe; it is shorthand for 2>&1 |. This implicit redirection of the standard error is performed after any redirections specified by the command. Also, as geirha points out, if you want to just get rid of stderr output, you would want to do something like find -name 'myfile.*' 2> /dev/null or perhaps find -name 'myfile.*' > /tmp/errorlog And note that if you have strings of commands, such as a find passing its output to xargs you would need to put the e
10, 2013 Authored by Dan Nanni Leave a comment If you have used find command on Linux, you probably have encountered the case where the command ends up producing an endless list of warning or error messages in its output, because you are "permission denied" to access certain files or directories. $ find / -name "my.txt" find: `./proc/18/task/18/fd': Permission denied find: `./proc/18/task/18/fdinfo': Permission denied find: `./proc/18/task/18/ns': Permission denied find: `./proc/18/fd': Permission denied find: `./proc/18/fdinfo': Permission denied find: `./proc/18/ns': Permission denied Such output is probably meaningless to you, so you may want to exclude these warning or error messages from the output, and get actual search result only. How can you suppress warnings or errors, and only get search result in find command? The find command sends any error or warning message to standard error output (i.e., stderr). So all you have to do to suppress these messages is to redirect stderr to /dev/null. The following is how to suppress all warnings or errors in find command. $ find . -name "my.txt" 2>/dev/null
If you want to capture stderr output in a separate file for later inspection, you can do the following instead. $ find . -name "my.txt" 2> find_error.txt If you want to exclude specific warnings only, you can filter out warning messages from stderr selectively by using grep, instead of redirecting the whole stderr. For example: $ find . -name "my.txt" 2>&1 | grep -v "Permission denied" The above command will suppress only "Permission denied" warning message, and show any other warning or error messages unfiltered. Subscribe to Xmodulo Do you want to receive Linux FAQs, detailed tutorials and tips published at Xmodulo? Enter your email address below, and we will deliver our Linux posts straight to your email box, for free. Delivery powered by Google Feedburner. Support Xmodulo Did you find this tutorial helpful? Then please be generous and support Xmodulo!The following two tabs change content below.BioLatest Posts Dan Nanni Dan Nanni is the founder and also a regular contributor of Xmodulo.com. He is a Linux/FOSS enthusiast who loves to get his hands dirty with his Linux box. He likes to procrastinate when he is supposed to be busy and productive. When he is otherwise free, he likes to watch movies and shop for the coolest gadgets. Latest posts by Dan Nanni (see all) How to open a TCP/UDP socket in a bash shell - May 24, 2016 How to enable incremental file sync for many users on Linux - April 24, 2016 How to build a kernel module with DKM