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Tilde Expansion

If a word begins with an unquoted tilde character (`~\fP'), all of the characters preceding the first unquoted slash (or all characters, if there is no unquoted slash) are considered a tilde-prefix\fP. If none of the characters in the tilde-prefix are quoted, the characters in the tilde-prefix following the tilde are treated as a possible login name\fP. If this login name is the null string, the tilde is replaced with the value of the shell parameter .SM .BR HOME . If .SM HOME is unset, the home directory of the user executing the shell is substituted instead. Otherwise, the tilde-prefix is replaced with the home directory associated with the specified login name.

If the tilde-prefix is a `~+', the value of the shell variable .SM PWD replaces the tilde-prefix. If the tilde-prefix is a `~-', the value of the shell variable .SM .BR OLDPWD , if it is set, is substituted. If the characters following the tilde in the tilde-prefix consist of a number N\fP, optionally prefixed by a `+' or a `-', the tilde-prefix is replaced with the corresponding element from the directory stack, as it would be displayed by the dirs builtin invoked with the tilde-prefix as an argument. If the characters following the tilde in the tilde-prefix consist of a number without a leading `+' or `-', `+' is assumed.

If the login name is invalid, or the tilde expansion fails, the word is unchanged.

Each variable assignment is checked for unquoted tilde-prefixes immediately following a : or .BR = . In these cases, tilde expansion is also performed. Consequently, one may use file names with tildes in assignments to .SM .BR PATH , .SM .BR MAILPATH , and .SM .BR CDPATH , and the shell assigns the expanded value.

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