BASH shell Environment variables

$*	Include all command-line arguments as a single text value
[Email protected]	Include all command-line arguments as separate text values
$#	Number of command-line arguments
$?	Exit status codes for most recently used front-end processes
$-	Current command option Tag
$$	Process ID (PID) of the current shell
$!	Recently executed background process PID
$	Command name from the command line
$_	The absolute path name of the shell
Bash	The full file name used to invoke the shell
Bash_argc	Number of arguments in the current child function
bash_argv	An array containing all the specified command-line arguments
Bash_command	The name of the command that is currently being executed
Bash_env	If set, each bash script will attempt to execute the first file starting with this variable before running.
Bash_execution_string	Commands used in the-C command-line option
Bash_lineno	An array containing the line numbers of each command in the script
Bash_rematch	An array containing the text elements that match the specified regular expression
Bash_source	An array containing the name of the source file where the function has been declared in the shell
Bash_subshell	Number of child shells produced by the current shell
Bash_version	Version number of the current bash shell instance
Bash_versinfo	A mutable array containing the major version number of the current bash shell instance with a good minor version number
COLUMNS	The terminal width of the terminal that contains the current bash shell instance
Comp_cword	The index value of the variable comp_words that contains the current cursor position
Comp_line	Current command line
Comp_point	The index of the current cursor position relative to the starting position of the current command
Comp_words	A mutable array containing all the words on the current command line
Compreply	Variable array containing possible padding words generated by shell functions
Dirstack	Variable array containing the current contents of the directory stack
Euid	Digital valid user ID for the current user
Fcedit	Default editor used by the FC command
Fignore	List of suffix names to ignore when colon-delimited file name completion is complete
FUNCNAME	The name of the currently executing shell function
Globignore	A colon-delimited list of patterns that defines a collection of filenames to ignore when the file name is expanded
GROUPS	Variable array containing list of current user groups
Histchars	Control history expanded characters up to 3 characters
Histcmd	The position of the current command in the history record
Histcontrol	Control which commands remain in the history list
Histfile	Save the file name of the Shell History list (by default,. basj_history)
Histfilesize	Keep the upper limit on the number of rows in the history record
Histignore	A colon-delimited list of patterns used to determine which commands are not stored in the history file
Histsize	How many records are saved in the history file
Hostfile	Contains the name of the file that the shell reads when it complements the host name
HOSTNAME	The name of the current host
HOSTTYPE	The machine that is currently running bash shell
Ignoreeof	The shell must receive the number of consecutive EOF characters before exiting, and if this value is not present, the default is 1
INPUTRC	ReadLine initial file name (default is. inputrc)
Lang	Language environment Classification for shells
Lc_all	Define a locale variable that overrides the lang variable
Lc_collate	Set the table order used when sorting string values
Lc_type	Determines how characters are interpreted when file name expansion and pattern matching
Lc_messages	Language environment variable that determines the double-quote string that interprets the pre-dollar ($) character
Lineno	The line number currently executing in the script
LINES	Defines the number of rows visible on the terminal
MACHTYPE	System types defined in the "cpu-Company-System" format
MailCheck	How often the shell looks at new messages (in seconds, the default is 60)
Oldpwd	The working directory before the Shell
Opterr	When set to 1 o'clock, bash shell displays the error generated by the getopts command
OSTYPE	Defines the operating system that the shell is running on
Pipestatus	Variable array containing the exit status code list for the front-end process
Posixly_correct	If set, bash will already be started in POSIX mode
PPID	The PID of the bash shell parent process
Prompt_command	is set, this command is executed before the command line main prompt is displayed.
PS1	Main command line prompt string
PS2	Times command line prompt string
PS3	Prompt for the Select command
PS4	If you use the Bashde-x parameter, the prompt that appears before the command line is displayed
Pwd	Current working directory
RANDOM	Returns the random number of a 0~32767 and assigns it to the seed of a random number generator
REPLY	Default variable for read command
SECONDS	Automatic shell boot to the present description; Assigning a value will recharge the counter
Shellopts	Colon-delimited list of open bash shell options
Shlvl	Indicates the shell level, with a new bash shell each time (boot self-increment)
TimeFormat	Specifies the format of the shell display time value
Tmout	The Select and read commands wait for how long (in seconds) without input. Default is zero, which means infinite length
Uid	Real user ID for the current user

BASH shell Environment variables