Linux Bash – Print STDOUT/STDERR and Write Them to a File in Bash

bashio-redirectionlinuxstderrstdout

Is there a way to have Bash redirect STDOUT/STDERR to a file yet still print them out to the terminal as well?

Best Answer

This will redirect both STDOUT and STDERR to the same file:

some_command 2>&1 | tee file.log

Example

$ touch foo; ls foo asfdsafsadf 2>&1 | tee file.log
ls: asfdsafsadf: No such file or directory
foo
$ cat file.log
ls: asfdsafsadf: No such file or directory
foo

Related Solutions

Linux – How to Redirect Output to a File and Stdout

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>&1 | tee outfile

2>&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>&1 | tee -a outfile

Bash – How to Redirect and Append Both Standard Output and Error to a File

cmd >>file.txt 2>&1

Bash executes the redirects from left to right as follows:

>>file.txt: Open file.txt in append mode and redirect stdout there.
2>&1: Redirect stderr to "where stdout is currently going". In this case, that is a file opened in append mode. In other words, the &1 reuses the file descriptor which stdout currently uses.

Best Answer

Example

Related Solutions

Linux – How to Redirect Output to a File and Stdout

Bash – How to Redirect and Append Both Standard Output and Error to a File

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