How to silence output in a Bash script

Question

I have a program that outputs to stdout and would like to silence that output in a Bash script while piping to a file   For example  running the program will output     myprogram   WELCOME TO MY PROGRAM   Done    I want the following script to not output anything to the terminal      bin bash myprogram  gt  sample s

User · Answer

For output only on error      so  command

User · Answer

If it outputs to stderr as well you ll want to silence that  You can do that by redirecting file descriptor 2     Send stdout to out log  stderr to err log myprogram  gt  out log 2 gt  err log    Send both stdout and stderr to out log myprogram  amp  gt  out log        New bash syntax myprogram  gt  out log 2 gt  amp 1    Older sh syntax    Log output  hide errors  myprogram  gt  out log 2 gt   dev null

User · Answer

If you want STDOUT and STDERR both  everything   then the simplest way is      bin bash myprogram  gt  amp  sample s   then run it like   script  and you will get no output to your terminal      the    amp   means STDERR and STDOUT  the  amp  also works the same way with a pipe    script   amp  sed that will send everything to sed

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Useful in scripts     Get only the STDERR in a file  while hiding any STDOUT even if the program to hide isn t existing at all  does not ever hang parent script   this alone was working   stty -echo  amp  amp    programMightNotExist 2 gt  errors log  amp  amp  stty echo     Detach completely and silence everything  even killing the parent script won t abort   prog       prog  lt  dev null  gt  dev null 2 gt  amp 1  amp

User · Answer

Redirect stderr to stdout  This will redirect the stderr  which is descriptor 2  to the file descriptor 1 which is the the stdout   2 gt  amp 1   Redirect stdout  to File  Now when perform this you are redirecting the stdout to the file sample s  myprogram  gt  sample s   Redirect stderr and stdout to File  Combining the two commands will result in redirecting both stderr and stdout to sample s  myprogram  gt  sample s 2 gt  amp 1   Redirect stderr and stdout to  dev null  Redirect to  dev null if you want to completely silent your application   myprogram  gt  dev null 2 gt  amp 1

User · Answer

Try with   myprogram  amp  gt  dev null   to get no output

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If you are still struggling to find an answer  specially if you produced a file for the output  and you prefer a clear alternative   echo  hi    grep  use this hack to hide the oputut

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Note  This answer is related to the question  How to turn off echo while executing a shell script Linux  which was in turn marked as duplicated to this one   To actually turn off the echo the command is      stty -echo    this is  for instance  when you want to enter a password and you don t want it to be readable  Remember to turn echo on at the end of your script  otherwise the person that runs your script won t see what he she types in from then on  To turn echo on run      stty echo

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All output   scriptname  amp  gt  dev null   Portable   scriptname  gt  dev null 2 gt  amp 1   Portable   scriptname  gt  dev null 2 gt  dev null   For newer bash  no portable    scriptname  amp  gt -

[bash] How to silence output in a Bash script?

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