How to redirect output to a file and stdout

Question

In bash  calling foo would display any output from that command on the stdout   Calling foo  gt  output would redirect any output from that command to the file specified  in this case  output     Is there a way to redirect output to a file and have it display on stdout

User · Answer

tee is perfect for this  but this will also do the job  ls -lr    gt  output   cat output

User · Answer

The command you want is named tee   foo   tee output file   For example  if you only care about stdout   ls -a   tee output file   If you want to include stderr  do   program  arguments     2 gt  amp 1   tee outfile   2 gt  amp 1 redirects channel 2  stderr standard error  into channel 1  stdout standard output   such that both is written as stdout  It is also directed to the given output file as of the tee command   Furthermore  if you want to append to the log file  use tee -a as   program  arguments     2 gt  amp 1   tee -a outfile

User · Answer

Another way that works for me is     lt command gt    amp  tee   lt outputFile gt    as shown in gnu bash manual  Example   ls   amp  tee files txt      If      amp     is used  command1   s standard error  in addition to its standard output  is connected to command2   s standard input through the pipe  it is shorthand for 2  amp 1    This implicit redirection of the standard error to the standard output is performed after any redirections specified by the command     For more information  refer redirection

User · Answer

Another handy alternative is to use screen command to run the main program and direct the stderr and stdout to a file  then use tail -f to view the file as it is being written to  You could also open another session if you don t want to use screen

User · Answer

Another way that works for me is     lt command gt    amp  tee   lt outputFile gt    as shown in gnu bash manual  Example   ls   amp  tee files txt      If      amp     is used  command1   s standard error  in addition to its standard output  is connected to command2   s standard input through the pipe  it is shorthand for 2  amp 1    This implicit redirection of the standard error to the standard output is performed after any redirections specified by the command     For more information  refer redirection

User · Answer

The command you want is named tee   foo   tee output file   For example  if you only care about stdout   ls -a   tee output file   If you want to include stderr  do   program  arguments     2 gt  amp 1   tee outfile   2 gt  amp 1 redirects channel 2  stderr standard error  into channel 1  stdout standard output   such that both is written as stdout  It is also directed to the given output file as of the tee command   Furthermore  if you want to append to the log file  use tee -a as   program  arguments     2 gt  amp 1   tee -a outfile

User · Answer

Using tail -f output should work

User · Answer

tee is perfect for this  but this will also do the job  ls -lr    gt  output   cat output

User · Answer

program  arguments     2 gt  amp 1   tee outfile   2 gt  amp 1 dumps the stderr and stdout streams  tee outfile takes the stream it gets and writes it to the screen and to the file  outfile    This is probably what most people are looking for  The likely situation is some program or script is working hard for a long time and producing a lot of output  The user wants to check it periodically for progress  but also wants the output written to a file   The problem  especially when mixing stdout and stderr streams  is that there is reliance on the streams being flushed by the program  If  for example  all the writes to stdout are not flushed  but all the writes to stderr are flushed  then they ll end up out of chronological order in the output file and on the screen   It s also bad if the program only outputs 1 or 2 lines every few minutes to report progress  In such a case  if the output was not flushed by the program  the user wouldn t even see any output on the screen for hours  because none of it would get pushed through the pipe for hours   Update  The program unbuffer  part of the expect package  will solve the buffering problem  This will cause stdout and stderr to write to the screen and file immediately and keep them in sync when being combined and redirected to tee  E g      unbuffer program  arguments     2 gt  amp 1   tee outfile

User · Answer

You can primarily use Zoredache solution  but If you don t want to overwrite the output file you should write tee with -a option as follow    ls -lR     tee -a output file

User · Answer

The command you want is named tee   foo   tee output file   For example  if you only care about stdout   ls -a   tee output file   If you want to include stderr  do   program  arguments     2 gt  amp 1   tee outfile   2 gt  amp 1 redirects channel 2  stderr standard error  into channel 1  stdout standard output   such that both is written as stdout  It is also directed to the given output file as of the tee command   Furthermore  if you want to append to the log file  use tee -a as   program  arguments     2 gt  amp 1   tee -a outfile

User · Answer

lt  command  gt    amp  tee filename   this will create a file  filename  with command status as a content  If a file already exists it will remove existed content and writes the command status    lt  command  gt    tee  gt  gt  filename   this will append status to the file but it doesn t print the command status on standard output  screen    I want to print something by using  echo  on screen and append that echoed data to a file  echo  hi there  Have to print this on screen and append to a file

User · Answer

program  arguments     2 gt  amp 1   tee outfile   2 gt  amp 1 dumps the stderr and stdout streams  tee outfile takes the stream it gets and writes it to the screen and to the file  outfile    This is probably what most people are looking for  The likely situation is some program or script is working hard for a long time and producing a lot of output  The user wants to check it periodically for progress  but also wants the output written to a file   The problem  especially when mixing stdout and stderr streams  is that there is reliance on the streams being flushed by the program  If  for example  all the writes to stdout are not flushed  but all the writes to stderr are flushed  then they ll end up out of chronological order in the output file and on the screen   It s also bad if the program only outputs 1 or 2 lines every few minutes to report progress  In such a case  if the output was not flushed by the program  the user wouldn t even see any output on the screen for hours  because none of it would get pushed through the pipe for hours   Update  The program unbuffer  part of the expect package  will solve the buffering problem  This will cause stdout and stderr to write to the screen and file immediately and keep them in sync when being combined and redirected to tee  E g      unbuffer program  arguments     2 gt  amp 1   tee outfile

User · Answer

You can do that for your entire script by using something like that at the beginning of your script        usr bin env bash  test x 1   x   x00   amp  amp  shift      set -o pipefail     exec 2 gt  amp 1    0    x00           tee mylogfile   exit           do whaetever you want   This redirect both stderr and stdout outputs to the file called mylogfile and let everything goes to stdout at the same time   It is used some stupid tricks     use exec without command to setup redirections  use tee to duplicates outputs  restart the script with the wanted redirections  use a special first parameter  a simple NUL character specified by the   string  special bash notation  to specify that the script is restarted  no equivalent parameter may be used by your original work   try to preserve the original exit status when restarting the script using the pipefail option    Ugly but useful for me in certain situations

User · Answer

lt  command  gt    amp  tee filename   this will create a file  filename  with command status as a content  If a file already exists it will remove existed content and writes the command status    lt  command  gt    tee  gt  gt  filename   this will append status to the file but it doesn t print the command status on standard output  screen    I want to print something by using  echo  on screen and append that echoed data to a file  echo  hi there  Have to print this on screen and append to a file

User · Answer

Another handy alternative is to use screen command to run the main program and direct the stderr and stdout to a file  then use tail -f to view the file as it is being written to  You could also open another session if you don t want to use screen

User · Answer

Bonus answer since this use-case brought me here   In the case where you need to do this as some other user   echo  some output    sudo -u some user tee  some path some file   Note that the echo will happen as you and the file write will happen as  some user  what will NOT work is if you were to run the echo as  some user  and redirect the output with     some file  because the file redirect will happen as you   Hint  tee also supports append with the -a flag  if you need to replace a line in a file as another user you could execute sed as the desired user

User · Answer

Using tail -f output should work

User · Answer

The command you want is named tee   foo   tee output file   For example  if you only care about stdout   ls -a   tee output file   If you want to include stderr  do   program  arguments     2 gt  amp 1   tee outfile   2 gt  amp 1 redirects channel 2  stderr standard error  into channel 1  stdout standard output   such that both is written as stdout  It is also directed to the given output file as of the tee command   Furthermore  if you want to append to the log file  use tee -a as   program  arguments     2 gt  amp 1   tee -a outfile

User · Answer

Something to add      The package unbuffer has support issues with some packages under fedora and redhat unix releases   Setting aside the troubles   Following worked for me  bash myscript sh 2 gt  amp 1   tee output log      Thank you ScDF  amp  matthew your inputs saved me lot of time

User · Answer

You can primarily use Zoredache solution  but If you don t want to overwrite the output file you should write tee with -a option as follow    ls -lR     tee -a output file

User · Answer

tee is perfect for this  but this will also do the job  ls -lr    gt  output   cat output

User · Answer

Using tail -f output should work

User · Answer

tee is perfect for this  but this will also do the job  ls -lr    gt  output   cat output

User · Answer

Something to add      The package unbuffer has support issues with some packages under fedora and redhat unix releases   Setting aside the troubles   Following worked for me  bash myscript sh 2 gt  amp 1   tee output log      Thank you ScDF  amp  matthew your inputs saved me lot of time

User · Answer

Bonus answer since this use-case brought me here   In the case where you need to do this as some other user   echo  some output    sudo -u some user tee  some path some file   Note that the echo will happen as you and the file write will happen as  some user  what will NOT work is if you were to run the echo as  some user  and redirect the output with     some file  because the file redirect will happen as you   Hint  tee also supports append with the -a flag  if you need to replace a line in a file as another user you could execute sed as the desired user

User · Answer

You can do that for your entire script by using something like that at the beginning of your script        usr bin env bash  test x 1   x   x00   amp  amp  shift      set -o pipefail     exec 2 gt  amp 1    0    x00           tee mylogfile   exit           do whaetever you want   This redirect both stderr and stdout outputs to the file called mylogfile and let everything goes to stdout at the same time   It is used some stupid tricks     use exec without command to setup redirections  use tee to duplicates outputs  restart the script with the wanted redirections  use a special first parameter  a simple NUL character specified by the   string  special bash notation  to specify that the script is restarted  no equivalent parameter may be used by your original work   try to preserve the original exit status when restarting the script using the pipefail option    Ugly but useful for me in certain situations

User · Answer

Using tail -f output should work

[linux] How to redirect output to a file and stdout

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