Error Output Redirection
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:
cmdRedirect Error Output Windows
> file ls > fileHowever, some time errors are displayed on redirect error output to /dev/null screen. How do I store and redirect output from the computer screen to a file on a Linux
Redirect Error Output To Stdout
or Unix-like 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 syntax is as follows to redirect error output powershell 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 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) redirect error output to file linux 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 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
>20.3. Applications
Redirect Error Output To File Unix
and any other open files, can be redirected. Redirection simply means capturing output from dos output redirection a file, command, program, script, or even code block within a script (see Example 3-1 and Example 3-2)
Output Redirection Java
and sending it as input to another file, command, program, or script.
Each open file gets assigned a file descriptor. [2] The file descriptors for stdin, stdout, and stderrhttp://www.cyberciti.biz/faq/linux-redirect-error-output-to-file/ > 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] This simplifies restoration to normal after complex redirection and reshuffling (see Example 20-1). COMMAND_OUTPUT > # Redirect stdout http://www.tldp.org/LDP/abs/html/io-redirection.html 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 to file "filename." 2>>filename # Redirect and append stderr to file "filename." &>filename # Redirect both stdout and stderr to file "filename." # This operator is now functional, as of Bash 4, final release. M>N # "M" is a file descriptor, which defaults to 1, if not explicitlya stderr redirect stderr to a stdout redirect stderr and stdout to a file redirect stderr and stdout to stdout redirect stderr and stdout to stderr http://tldp.org/HOWTO/Bash-Prog-Intro-HOWTO-3.html 1 'represents' stdout and 2 stderr. A little note for seeing this things: with the less command you can view both stdout (which will remain on the buffer) and the stderr https://support.microsoft.com/en-us/kb/110930 that will be printed on the screen, but erased as you try to 'browse' the buffer. 3.2 Sample: stdout 2 file This will cause the ouput of a program to be error output written to a file.
ls -l > ls-l.txtHere, a file called 'ls-l.txt' will be created and it will contain what you would see on the screen if you type the command 'ls -l' and execute it. 3.3 Sample: stderr 2 file This will cause the stderr ouput of a program to be written to a file.
grep da * redirect error output 2> grep-errors.txtHere, a file called 'grep-errors.txt' will be created and it will contain what you would see the stderr portion of the output of the 'grep da *' command. 3.4 Sample: stdout 2 stderr This will cause the stderr ouput of a program to be written to the same filedescriptor than stdout.
grep da * 1>&2Here, the stdout portion of the command is sent to stderr, you may notice that in differen ways. 3.5 Sample: stderr 2 stdout This will cause the stderr ouput of a program to be written to the same filedescriptor than stdout.
grep * 2>&1Here, the stderr portion of the command is sent to stdout, if you pipe to less, you'll see that lines that normally 'dissapear' (as they are written to stderr) are being kept now (because they're on stdout). 3.6 Sample: stderr and stdout 2 file This will place every output of a program to a file. This is suitable sometimes for cron entries, if you want a command to pass in absolute silence.
rm -f $(find / -name core) &>360 games PC games Windows games Windows phone games Entertainment All Entertainment Movies & TV Music Business & Education Business Students & educators Developers Sale Sale Find a store Gift cards Products Software & services Windows Office Free downloads & security Internet Explorer Microsoft Edge Skype OneNote OneDrive Microsoft Health MSN Bing Microsoft Groove Microsoft Movies & TV Devices & Xbox All Microsoft devices Microsoft Surface All Windows PCs & tablets PC accessories Xbox & games Microsoft Lumia All Windows phones Microsoft HoloLens For business Cloud Platform Microsoft Azure Microsoft Dynamics Windows for business Office for business Skype for business Surface for business Enterprise solutions Small business solutions Find a solutions provider Volume Licensing For developers & IT pros Develop Windows apps Microsoft Azure MSDN TechNet Visual Studio For students & educators Office for students OneNote in classroom Shop PCs & tablets perfect for students Microsoft in Education Support Sign in Cart Cart Javascript is disabled Please enable javascript and refresh the page Cookies are disabled Please enable cookies and refresh the page CV: {{ getCv() }} English (United States) Terms of use Privacy & cookies Trademarks © 2016 Microsoft