\before line feeds to break lines in
[ "$filename" = "$otherfile" ]
[ "$filename" = \ "$otherfile" ]
[[ ]]] can include line breaks anywhere, but
[ ] requires that you escape them. If you are writing a multi-line
[ .. ] statement, make sure to include these escapes. If the
[ ] is supposed to be on a single line, make sure the
] is there.
ShellCheck is a static analysis tool for shell scripts. This page is part of its documentation.