Bash 5 reference · Shell Builtins and Syntax

redirection (Bash syntax)

Send output to files, read input from files, merge stderr into stdout, and discard output with /dev/null.

Bash 5

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Syntax

cmd > file   cmd >> file   cmd 2> file   cmd &> file   cmd 2>&1   cmd < file

Parameter	Description
`>`	Overwrite a file with stdout.
`>>`	Append stdout.
`2>&1`	Send stderr where stdout goes.
`&>`	Both stdout and stderr to a file.
`<( cmd )`	Process substitution: a command's output as a file.

Overwrite, append, stderr

echo one > out.txt; echo two >> out.txt
ls nope 2> err.txt || true
wc -l < out.txt; grep -c 'nope' err.txt

Output

2
1

Run this on your computer — see “Get Started” for setup.

Process substitution

diff <(printf 'a\nb\n') <(printf 'a\nc\n') || true

Output

2c2
< b
---
> c

Run this on your computer — see “Get Started” for setup.

here-document · Feed multiple lines to a command with <<EOF; quote the marker to stop variable expansion, use <<- to strip tabs.
Bash Redirection and Pipes · tutorial