$IFS Environment Varable

The \$IFS environment variable in Linux stands for "Internal Field Separator". It is used by the shell to determine how to do word splitting, i.e., how to recognize word boundaries. In essence, $IFS defines a string of characters that the shell treats as delimiters between words or fields.

By default, $IFS contains three characters: space, tab, and newline. This means that in its default state, the shell will split words or fields on spaces, tabs, and newlines. You can change the value of $IFS to alter the behavior of shell scripts or commands. For instance, if you set IFS=,, the shell will treat commas as the delimiter for splitting words.

It's commonly used in shell scripts and command lines, especially when reading data from a file or processing input strings. For example, when parsing CSV files, setting IFS to a comma is useful. Modifying $IFS can significantly change the behavior of scripts and commands. It should be done cautiously, and typically, IFS is restored to its original state after its custom use in a script.

Changes to IFS in a subshell do not affect the parent shell. So, scripts often modify IFS in a subshell to avoid side effects. It's also used in command-line arguments and in parsing file paths, where directories and filenames are separated by specific delimiters (like / in file paths).