Linux Redirect Error Output To File

I am a new Ubuntu Linux and bash shell user. I also know how to redirect output from display/screen to a file using the following syntax:

cmd > file
ls > file

However, some time errors are displayed on screen. How do I store and redirect output from the computer screen to a file on a Linux or Unix-like systems?

Tutorial details
DifficultyEasy (rss)
Root privilegesNo
RequirementsNone
Estimated completion time2m

Bash / ksh and other modern shell on Linux has three file descriptors:

  1. stdin (0)
  2. stdout (1)
  3. stderr (2)

Syntax To redirect all output to file

The syntax is as follows to redirect output (stdout) as follows:

  command-name >  output.txt command-name >  stdout.txt

Syntax To redirect all error to file

The syntax is as follows to redirect errors (stderr) as follows:

  command-name 2> errors.txt command-name 2> stderr.txt

Syntax to redirect both output (stdout) and errors (stderr) to different files

The syntax:

  command1 > out.txt 2> err.txt command2 -f -z -y > out.txt 2> err.txt

Syntax to redirect both output (stdout) and errors (stderr) to same file

The syntax is:

  command1 > everything.txt 2>&1 command1 -arg > everything.txt 2>&1

Syntax to redirect errors (stderr) to null or zero devices

Data written to a null or zero special file is discarded by your system. This is useful to silence out errors (also know as ‘error spam’):

  command1 2> /dev/null command1 2> /dev/zero command2 -arg 2> /dev/null command2 -arg 2> /dev/zero

Tip: Use tee command to redirect to both a file and the screen same time

The syntax is:

  command1 |& tee log.txt ## or ## command1 -arg |& tee log.txt ## or ## command1 2>&1 | tee log.txt

Another usage:

#!/bin/bash # My script to do blah ... foo(){  : } 2>&1 | tee foo.log

OR

#!/bin/bash # My script to do blah ... {    command1    command2 } 2>&1 | tee script.log

 

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