linux_wiki:use_input-output_redirection

Use Input-output Redirection

General Information

Using input/output redirection (>, », |, 2>, etc.).


'>' Redirect standard output to a file, overwrite contents

cat /etc/system-release > info.txt


'»' Redirect standard output to file, append to file

tail /etc/passwd >> info.txt


'|' Piping output to other commands

cat /etc/passwd | wc -l
  • Counts the number of lines in /etc/passwd


'2>' Redirect standard error

ssh admin@webserver01.com "uptime" 2>/dev/null
  • SSH to webserver01.com, issue the uptime command, send standard errors to /dev/null (to nowhere)


Redirect both standard error and standard output

ssh admin@webserver01.com "uptime" &> results.log


Redirect standard error to standard out

cat /etc/system-release /etc/Red 2>&1 | grep Red
  • Standard output can be passed through a pipe to the next command. By redirecting standard error to standard output, any error messages are successfully sent through as well.

  • linux_wiki/use_input-output_redirection.txt
  • Last modified: 2019/05/25 23:50
  • (external edit)