- Standard Input (stdin): default to the keyboard
- Standard Output (stdout): default to the monitor screen
- Standard Error (stderr): default to the monitor's screen
- 0: stdin
- 1: stdout
- 2: stderr
To redirect a process's output to a file (only normal messages, no errors):Standard input can also be represented by '-'.
This is equivalent to
copy con outputfilein DOS.
$ command > outputfile $ command - > outputfile
To direct a file as standard input:
command < inputfile
To direct standard input to a file:
cat > outputfile
To direct a process's output to another process (command) as standard input, use pipe:
command_out | command_in
cat filename | more
To direct error to a file:
$ command 2>errors.txt # 2 indicates the error stream in Linux $ command 2>/dev/null # /dev/null is a device where anything you send simply disappears.
To direct both standard output and error to a file:
$ command > error.log 2>&1 # '&1' represent stdout.To direct stdout to output.log and stderr to error.log, and print only error to the screen:
$ command 2>&1 > output.log | tee error.log # append error to the same output.log file instead of error.log. $ command 2>&1 > output.log | tee -a output.log