SC3021

Note: ShellCheck 0.8.0 and below would trigger this warning on the perfectly POSIX compatible construct >& fd. If you are using >& to copy an integer file descriptor, please ignore this warning.

# Writing to a filename
mycommand >& log.txt

mycommand > log.txt 2>&1

The following construct is also fine, as it uses an integer file descriptor instead of a filename:

fd=3
mycommand >& $fd

There are two forms of the >& file descriptor operator:

• >& integer such as >& 3 is a POSIX compatible synonym for 1>&3
• >& filename such as >& log.txt is a Bash specific synonym for > log.txt 2>&1

If (and only if) you are using the latter form, write it out as shown in the correct example to ensure portability.

ShellCheck 0.8.0 and below incorrectly emits this warning for constructs like >& $var, even though this would be POSIX compatible when $var is an integer. In such cases, please ignore this warning.

• Shellcheck issue #2520
• Help by adding links to BashFAQ, StackOverflow, man pages, POSIX, etc!