See also Redirection cheatsheet under Files.

Piping

Sending input to another command.

$ echo -e 'abc\ndef' | wc -l
2

Send literal output of a file listing command to the wc command.

$ find . -type f | wc -l

Send it to the less command.

$ find . -type f | less

Subshell

Evaluate and send the file list output to the wc command.

wc -l $(find . -type f)

Subshell and pipe

Chain more tools.

head $(find . -type f) | less

Piping and exit code

Default

The shell does not exit if the command that fails is: (…)

any command in a pipeline but the last, or if the command’s return status is being inverted with !.

The exit status of a pipeline is the exit status of the last command in the pipeline.

e.g. This script will see cat as a success and then run the echo.

#!/usr/bin/env bash

set -e

non_existent_cmd | another_non_existent_cmd | cat
echo "Hello"

bash: line 3: non_existent_cmd: command not found
bash: line 3: another_non_existent_cmd: command not found
Hello

Pipe fail

If the pipefail is enabled, the pipeline;s return status is the value of the last (rightmost) command to exit with a non-zero status, or zero if all commands exit successfully.

See more info in the Options cheatsheet.

set -o pipefail

e.g. This script will exit before running the echo.

#!/usr/bin/env bash

set -eo pipefail

non_existent_cmd | another_non_existent_cmd | cat
echo "Hello"