Linux Pocket Guide, 2nd Edition

Whitespace and Linebreaks

bash shell scripts are very sensitive to whitespace and linebreaks. Because the “keywords” of this programming language are actually commands evaluated by the shell, you need to separate arguments with whitespace. Likewise, a linebreak in the middle of a command will mislead the shell into thinking the command is incomplete. Follow the conventions we present here and you should be fine.

If you must break a long command into multiple lines, end each line (except the last) with a single \ character, which means “continued on next line”:

$ grep abcdefghijklmnopqrstuvwxyz file1 file2 \
file3 file4