Bash Shell Redirects

Shell redirects let you control where command output goes. Instead of everything landing on your terminal, you can write stdout or stderr to a file, swap the two streams, or combine them. Here is a compact reference for the operators you will reach for most often.

Redirect stdout to a file

command > output.txt

The single > operator sends standard output (file descriptor 1) to the named file. If the file already exists, its contents are overwritten.

Append stdout to a file

command >> output.txt

The double >> operator does the same thing as > but appends to the file instead of truncating it. Handy for logging over time.

Redirect stderr to stdout

command 2>&1

File descriptor 2 is stderr. The 2>&1 syntax points stderr to wherever stdout is currently going. Combined with a file redirect, you capture both streams:

command > output.txt 2>&1

Redirect stdout to stderr

command 1>&2

The reverse of the previous case. stdout is sent to the stderr stream. Useful when a parent process is capturing stderr and you want stdout to follow.

Redirect stderr to a file

command 2> errors.log

Sends only stderr to the named file while stdout continues to the terminal.

Redirect stdout to a file

command 1> output.txt

Explicit form of the > operator. You rarely need to write 1> because stdout is the default, but it makes the intent clear in scripts.

Quick reference table

A few practical tips

• Order matters. command > out.txt 2>&1 captures both streams into out.txt. Swapping to command 2>&1 > out.txt sends stderr to the terminal and only stdout to the file.
• Use >> in cron jobs and long-running scripts so you do not lose earlier log entries.
• If you want to discard output entirely, redirect to /dev/null: command > /dev/null 2>&1.

These six operators cover the vast majority of day-to-day shell scripting. Once the file-descriptor model clicks, the rest of bash redirection (process substitution, here-docs, tee) builds naturally on top of them.

• Technology
• How-To

• Bash
• SysAdmin