Input Field Separators

The value of IFS, (in the bash shell) typically includes the space, tab, and the newline characters by default.

If IFS is unset, or its value is exactly , the default, then sequences of , , and at the beginning and end of the results of the previous expansions are ignored, and any sequence of IFS characters not at the beginning or end serves to delimit words.

According to the Open Group Base Specifications, IFS is an abbreviation for "input field separators.

"[1] A newer version of this specification mentions that "this name is misleading as the IFS characters are actually used as field terminators.

A program with root permissions could be fooled into executing user-supplied code if it ran (for instance) system("/bin/mail") and was called with $IFS set to "/", in which case it would run the program "bin" (in the current directory and thus writable by the user) with root permissions.