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10.4.5 Details of Tilde Expansion

It’s a standard part of shell syntax that you can use ‘~’ at the beginning of a file name to stand for your own home directory. You can use ‘~user’ to stand for user’s home directory.

Tilde expansion is the process of converting these abbreviations to the directory names that they stand for.

Tilde expansion applies to the ‘~’ plus all following characters up to whitespace or a slash. It takes place only at the beginning of a word, and only if none of the characters to be transformed is quoted in any way.

Plain ‘~’ uses the value of the environment variable HOME as the proper home directory name. ‘~’ followed by a user name uses getpwname to look up that user in the user database, and uses whatever directory is recorded there. Thus, ‘~’ followed by your own name can give different results from plain ‘~’, if the value of HOME is not really your home directory.