echo that outputs to stderr

Question

Is there a standard Bash tool that acts like echo but outputs to stderr rather than stdout   I know I can do echo foo 1 gt  amp 2 but it s kinda ugly and  I suspect  error prone  e g  more likely to get edited wrong when things change

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Mac OS X  I tried the accepted answer and a couple of other answers and all of them resulted in writing STDOUT not STDERR on my Mac   Here is a portable way to write to standard error using Perl   echo WARNING    perl -ne  print STDERR

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If you don t mind logging the message also to syslog  the not so ugly way is   logger -s  msg   The -s option means   Output the message to standard error as well as to the system log

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Since 1 is the standard output  you do not have to explicitly name it in front of an output redirection like  gt   Instead  you can simply type  echo This message goes to stderr  gt  amp 2  Since you seem to be worried that 1 gt  amp 2 will be difficult for you to reliably type  the elimination of the redundant 1 might be a slight encouragement to you

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No  that s the standard way to do it   It shouldn t cause errors

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Note  I m answering the post- not the misleading vague  echo that outputs to stderr  question  already answered by OP    Use a function to show the intention and source the implementation you want  E g      bin bash    -x error handling    amp  amp    error handling  filename  foobar txt  config error  filename  invalid value    output xml error  No such account   debug output  Skipping cache   log error  Timeout downloading archive   notify admin  Out of disk space    fatal  failed to open logger     And error handling being   ADMIN EMAIL root localhost  config error     filename   1   shift  echo  Config error in  filename      2 gt  amp 1     output xml error     echo   lt error gt    lt  error gt   2 gt  amp 1     debug output         DEBUG    1     amp  amp  echo  DEBUG          log error     logger -s          fatal     which logger  gt  dev null  amp  amp  logger -s  FATAL         echo  FATAL       exit 100     notify admin     echo        mail -s  Error from script    ADMIN EMAIL       Reasons that handle concerns in OP    nicest syntax possible  meaningful words instead of ugly symbols  harder to make an error  especially if you reuse the script  it s not a standard Bash tool  but it can be a standard shell library for you or your company organization   Other reasons    clarity - shows intention to other maintainers speed - functions are faster than shell scripts reusability - a function can call another function configurability - no need to edit original script debugging - easier to find the line responsible for an error  especially if you re deadling with a ton of redirecting filtering output  robustness - if a function is missing and you can t edit the script  you can fall back to using external tool with the same name  e g  log error can be aliased to logger on Linux  switching implementations - you can switch to external tools by removing the  x  attribute of the library output agnostic - you no longer have to care if it goes to STDERR or elsewhere personalizing - you can configure behavior with environment variables

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This is a simple STDERR function  which redirect the pipe input to STDERR      bin bash                                                                   This function redirect the pipe input to STDERR       param stream    return string   function STDERR       cat - 1 gt  amp 2       remove the directory  bubu if rm  bubu 2 gt  dev null  then     echo  Bubu is gone   else     echo  Has anyone seen Bubu     STDERR fi     run the bubu sh and redirect you output tux earth      bubu sh  gt  tmp bubu log 2 gt  tmp bubu err

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My suggestion     echo  my errz   gt  gt   proc self fd 2   or   echo  my errz   gt  gt   dev stderr   echo  my errz   gt   proc self fd 2 will effectively output to stderr because  proc self is a link to the current process  and  proc self fd holds the process opened file descriptors  and then  0  1  and 2 stand for stdin  stdout and stderr respectively   The  proc self link doesn t work on MacOS  however   proc self fd   is available on Termux on Android  but not  dev stderr  How to detect the OS from a Bash script  can help if you need to make your script more portable by determining which variant to use

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Here is a function for checking the exit status of the last command  showing error and terminate the script  or exit         local exit status        local message         if    quot  exit status quot  -gt 0       then         echo  quot   date    F  T      basename  quot  0 quot   sh    ERROR   message quot   gt  amp 2         exit  quot  exit status quot      fi    Usage  gzip  quot  data dir quot      or exit  quot Cannot gzip  data dir quot   rm -rf  quot  junk quot      or exit Cannot remove  junk folder  The function prints out the script name and the date in order to be useful when the script is called from crontab and logs the errors  59 23        my backup sh 2 gt  gt   my error log

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You could do this  which facilitates reading    gt  amp 2 echo  error     gt  amp 2 copies file descriptor  2 to file descriptor  1  Therefore  after this redirection is performed  both file descriptors will refer to the same file  the one file descriptor  2 was originally referring to  For more information see the Bash Hackers Illustrated Redirection Tutorial

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read is a shell builtin command that prints to stderr  and can be used like echo without performing redirection tricks   read -t 0 1 -p  This will be sent to stderr    The -t 0 1 is a timeout that disables read s main functionality  storing one line of stdin into a variable

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Another option  echo foo  gt  gt  dev stderr

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Make a script     bin sh echo    1 gt  amp 2   that would be your tool   Or make a function if you don t want to have a script in separate file

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Don t use cat as some have mentioned here  cat is a program while echo and printf are bash  shell  builtins  Launching a program or another script  also mentioned above  means to create a new process with all its costs  Using builtins  writing functions is quite cheap  because there is no need to create  execute  a process  -environment   The opener asks  quot is there any standard tool to output  pipe  to stderr quot   the short answer is   NO     why      redirecting pipes is an elementary concept in systems like unix  Linux     and bash  sh  builds up on these concepts  I agree with the opener that redirecting with notations like this   amp 2 gt 1 is not very pleasant for modern programmers  but that s bash  Bash was not intended to write huge and robust programs  it is intended to help the admins to get there work with less keypresses  -  And at least  you can place the redirection anywhere in the line    echo This message  gt  amp 2 goes to stderr  This message goes to stderr

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Another option that I recently stumbled on is this                 echo  First error line          echo  Second error line          echo  Third error line         gt  amp 2   This uses only Bash built-ins while making multi-line error output less error prone  since you don t have to remember to add  amp  gt 2 to every line

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You could define a function   echoerr     echo      1 gt  amp 2    echoerr hello world   This would be faster than a script and have no dependencies   Camilo Martin s bash specific suggestion uses a  here string  and will print anything you pass to it  including arguments  -n  that echo would normally swallow   echoerr     cat  lt  lt  lt       1 gt  amp 2      Glenn Jackman s solution also avoids the argument swallowing problem   echoerr     printf   s n        gt  amp 2

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Combining solution suggested by James Roth and Glenn Jackman   add ANSI color code to display the error message in red    echoerr     printf   e 31 1m s e 0m n        gt  amp 2       if somehow  e is not working on your terminal  use  u001b instead   echoerr     printf   u001b 31 1m s u001b 0m n        gt  amp 2     echoerr  This error message should be RED

[bash] echo that outputs to stderr

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