# Number of arguments given to current process.
@ Command-line arguments to current process. Inside double quotes, expands to individual arguments.
* Command-line arguments to current process. Inside double quotes, expands to a single argument.
- (hyphen) Options given to shell on invocation.
? Exit status of previous command.
$ Process ID of shell process.
0 (zero) The name of the shell program.
! Process ID of last background command. Use this to save process ID numbers for later use with the wait
ENV Used only by interactive shells upon invocation; the value of$ENV is parameter-expanded. The result
should be a full pathname for a file to be read and executed at startup. This is an XSI requirement.
HOME Home (login) directory.
IFS Internal field separator; i.e., the list of characters that act as word separators. Normally set to space, tab,
LANG Default name of current locale; overridden by the otherLC_* variables.
LC_ALL Name of current locale; overrides LANG and the otherLC_* variables.
LC_COLLATE Name of current locale for character collation (sorting) purposes.