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Redirezione Standard Error Linux

updated March 12, 2008 in BASH Shell, Linux, UNIX Q. How do I redirect stderr to stdout? How do I redirect stderr to a file? A. Bash and print stderr bash other modern shell provides I/O redirection facility. There are 3 default standard files (standard print stdout perl streams) open: [a] stdin - Use to get input (keyboard) i.e. data going into a program.

[b] stdout - Use perl redirect stderr to write information (screen) [c] stderr - Use to write error message (screen) Understanding I/O streams numbers The Unix / Linux standard I/O streams with numbers: Handle Name Description 0 stdin Standard input 1

Perl Redirect Stderr To Stdout

stdout Standard output 2 stderr Standard error Redirecting the standard error stream to a file The following will redirect program error message to a file called error.log: $ program-name 2> error.log
$ command1 2> error.log Redirecting the standard error (stderr) and stdout to file Use the following syntax: $ command-name &>file OR $ command > file-name 2>&1 Another useful example: # find /usr/home -name .profile 2>&1 | more Redirect perl redirect stderr to null stderr to stdout Use 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 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 am What this mean? $ command > file-name 2>&1 Reply Link Hesham M January 22, 2014, 3:34 pm This 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 am Sayed: that line means execute the command while redirecting

>20.3. Applications

There are always three default files [1] open, stdin (the keyboard), stdout (the screen), and stderr (error perl redirect stdout to variable messages output to the screen). These, and any other open files, can

Print Stderr C

be redirected. Redirection simply means capturing output from a file, command, program, script, or even code block within

Perl Printf Stderr

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 a file descriptor. http://www.cyberciti.biz/faq/redirecting-stderr-to-stdout/ [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] This simplifies restoration http://www.tldp.org/LDP/abs/html/io-redirection.html 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 to file "filename." 2>>filename # Redirect and append

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 Learn more http://unix.stackexchange.com/questions/80629/redirect-both-stderr-and-stdout-to-dev-null-with-bin-sh about hiring developers or posting ads with us Unix & Linux Questions Tags Users Badges Unanswered http://www.pluto.it/files/ildp/HOWTO/Bash-Prog-Intro-HOWTO/Bash-Prog-Intro-HOWTO-3.html Ask Question _ Unix & Linux Stack Exchange is a question and answer site for users of Linux, FreeBSD and other Un*x-like operating systems. 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 Redirect both stderr and stdout to /dev/null with perl redirect /bin/sh up vote 20 down vote favorite 5 Tried all sorts of ways to redirect both stdout and stderr to /dev/null without any success. I have almost my entire life run bash which i've never had this issue with but for once in BSD i'm stuck with /bin/sh. What i've tried: if ls ./python* 2> /dev/null; then echo found Python fi Which works, if Python is not present it will mute the error messages from ls. However, if python.tgz perl redirect stderr is present a line with be outputted which looks like this: # ./test.sh ./python-2.7.3p1.tgz And i've tried: if ls ./python* &> /dev/null; then echo found Python fi and if ls ./python* 2>1 > /dev/null; then echo found Python fi and if ls ./python* > /dev/null; then echo found Python fi Nothing really works. I can only redirect one of the outputs, not both at the same time. shell io-redirection openbsd share|improve this question asked Jun 25 '13 at 19:12 Torxed 73031029 add a comment| 1 Answer 1 active oldest votes up vote 37 down vote accepted I believe what you are looking for is: ls good bad >/dev/null 2>&1 You have to redirect stdout first before duplicating it into stderr; if you duplicate it first, stderr will just point to what stdout originally pointed at. In bash you can do this with &>/dev/null but that's a bash extension. share|improve this answer edited Jun 26 '13 at 7:49 l0b0 17.6k1069145 answered Jun 25 '13 at 19:22 rici 6,0881725 1 Indeed, i read the bourn shell manual. It stated that later versions of /bin/sh have implemented the &>/dev/null syntax, aparently not so or i have a older version (which i can't echo in any way, running OpenBSD 5.3 tho so should be sufficient) –Torxed Jun 25 '13 at 19:29 4 @Torxed, OpenBSD's sh is based on pdksh. There's no more Bourne shell nowadays. csh introduced >& a

file redirigere stdout verso stderr redirigere stderr verso stdout redirigere stderr e stdout verso un file redirigere stderr e stdout verso stdout redirigere stderr e stdout verso stderr 1 'rappresenta' stdout e 2 stderr. Una piccola nota per vedere queste cose: con il comando less puoi visualizzare sia stdout (che resterà nel buffer) che lo stderr che verrà stampato sullo schermo, ma eliminato non appena tenterai di 'sfogliare' il buffer. 3.2 Esempio: stdout verso file Questo farà sì che l'output di un programma venga scritto su un file.

 ls -l > ls-l.txt 
Qui, un file chiamato 'ls-l.txt' verrà creato e conterrà ciò che vedresti sullo schermo digitando il comando 'ls -l' ed eseguendolo. 3.3 Esempio: stderr verso file Questo farà sì che l'output di stderr di un programma venga scritto su un file.
 grep da * 2> grep-errors.txt 
Qui, un file chiamato 'grep-errors.txt' sarà creato e conterrà ciò che vedresti come porzione di stderr dell'output del comando 'grep da *'. 3.4 Esempio: stdout verso stderr Questo farà sì che l'output di stderr di un programma venga scritto sul medesimo filedescriptor di stdout.
 grep da * 1>&2 
Qui, la porzione di stdout del comando è inviata a stderr, puoi accorgertene in diversi modi. 3.5 Esempio: stderr verso stdout Questo farà sì che l'output di stderr di un programma venga scritto sul medesimo filedescriptor di stdout.
 grep * 2>&1 
Qui, la porzione di stderr del comando è inviata a stdout, se fai una pipe verso less, noterai che righe le quali normalmente 'scomparirebbero' (poiché sono scritte su stderr) ora vengono tenute (perché si trovano su stdout). 3.6 Esempio: stderr e stdout verso file Questo porterà ogni output di un programma su un file. Può risultare a volte utile per cron, se vuoi che un comando passi in assoluto silenzio.
 rm -f $(find / -name core) &> /dev/null 
Questo (pensando a cron) eliminerà ogni file chiamato 'core' in qualsiasi directory. Osserva che dovresti essere piuttosto sicuro di cosa sta facendo un comando, prima di eliminarne ogni output. Avanti Indietro Indice

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