std_redirect.md

stdin, stdout, stderr

Stream

• 0 stdin
• 1 stdout
• 2 stderr
• > /dev/tty - print to screen which cannot be passed directly

Redirect

• | pipe
  • command1 | command2 : stdout pipe to command2
• > pass content to file
  • command > file : stdout to file (1>)
  • command 2> file : stderr 2 to file
  • command &> file : stderr 2 + stdout 1 to file (2>&1)
  • command &> /dev/null : suppress all
• < pass content from file
  • readarrary -t array < file
• << heredoc
  • var=$( cat << EOF - set var
  • cat << EOF > file - pass content to file
• <<< herestring - pass content to command
  • command2 <<< $( command1 ) : multiline stdout to command2
  • command <<< "$var" : read variable as multiline stdin (here string)
• script -c - capture everything on screen to file. (for commands not stdout to var)
  • script -c 'command' file - capture /dev/tty to file

accummulate stdout

{
  command1
  command2
  command3
} > file