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Linux-Environment
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This section collects info about common Linux shell environment variables. As a first step it is crowded by the variables found scanning the busybox and bash executables as well as the uClibc, glibc and musl libraries of each Firmware for all possible variables found in their source code. Some variables also appear in AVM-Environment and in CGI-Environment, which are in fact all the same, but at different positions and with different inheritance so they get own articles, and are cross referenced in the name collision header of each affected article. See also GNU Bash-Variables and variables.
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Linux-Environment[edit]
Daily updated index of all Linux shell variables found scanning Firmware-Probes . Last update: 2025-05-26 04:04 GMT.
The label (linenv) in the Variable column shows there are other objects in this wiki using this name.
The Mod column shows the amount of models using the respective variable. Click the column header to sort by this number.
Goto: A - B - C - D - E - F - G - H - I - J - K - L - M - N - O - P - Q - R - S - T - U - V - W - X - Y - Z - Index
| Variable | Mod | Firmware | Description | Type | Origin |
|---|---|---|---|---|---|
| ACTION | The action to perform for mdev. | ||||
| auto_resume | 4 | 7.04 - 7.90 | Controls how the shell interacts with the user and job control. | Text | bash |
| BASH | 4 | 7.04 - 7.90 | The full pathname used to execute the current instance of Bash. | Text | bash |
| BASHOPTS | 4 | 7.04 - 7.90 | Colon-separated list of enabled shell options maintained by shopt. | Text | bash |
| BASHPID | 4 | 7.04 - 7.90 | Expands to the process ID of the current Bash process. | Text | bash |
| BASH_ALIASES | 4 | 7.04 - 7.90 | An associative array of aliases as maintained by alias. | Text | bash |
| BASH_ARGC | 4 | 7.04 - 7.90 | An array of the number of parameters in each frame of the bash stack. | Text | bash |
| BASH_ARGV | 4 | 7.04 - 7.90 | An array of the parameters in each frame of the bash stack. | Text | bash |
| BASH_CMDS | 4 | 7.04 - 7.90 | An array of the builtin Bash-Commands. | Text | bash |
| BASH_COMMAND | 4 | 7.04 - 7.90 | The command currently being executed. | Text | bash |
| BASH_COMPAT | 4 | 7.04 - 7.90 | The value to set the shell's compatibility level. | Text | bash |
| BASH_ENV | 4 | 7.04 - 7.90 | The path where Bash startup scripts are located. | Text | bash |
| BASH_EXECUTION_STRING | 4 | 7.04 - 7.90 | The command argument to the 'bash -c' invocation option. | Text | bash |
| BASH_LINENO | 4 | 7.04 - 7.90 | An array of line numbers in source files. | Text | bash |
| BASH_LOADABLES_PATH | 4 | 7.14 - 7.90 | Array of directories to search for loadable builtins maintained by enable. | Text | bash |
| BASH_REMATCH | 4 | 7.04 - 7.90 | An array assigned by the '=~' binary operator to the '[[' conditional command. | Text | bash |
| BASH_SOURCE | 4 | 7.04 - 7.90 | An array of source filenames of functions named in FUNCNAME. | Text | bash |
| BASH_SUBSHELL | 4 | 7.04 - 7.90 | Bash nesting depth. 0 = not a subshell. | Text | bash |
| BASH_VERSINFO | 4 | 7.04 - 7.90 | Readonly array of version informations for this instance of Bash. | Text | bash |
| BASH_VERSION | 4 | 7.04 - 7.90 | The version number of the current instance of Bash. | Text | bash |
| BASH_XTRACEFD | 4 | 7.04 - 7.90 | File descriptor number for trace output. | Text | bash |
| BC_ENV_ARGS | TODO | ||||
| bootchart_init | TODO | ||||
| CDPATH | 4 | 7.04 - 7.90 | The search path for the cd command. | Text | bash |
| CHARSET | Decoded MIME charset for reformime, defaults to build option. | ||||
| CHILD_MAX | 4 | 7.04 - 7.90 | Set the number of exited child status values for the shell. | Text | bash |
| COLUMNS | 4 | 7.04 - 7.90 | The number of characters per line on the console window. | Text | bash |
| COMPREPLY | 4 | 7.04 - 7.90 | An array of possible completions generated by the programmable completion facility. | Text | bash |
| COMP_CWORD | 4 | 7.04 - 7.90 | An index into COMP_WORDS of the word containing the current cursor position. | Text | bash |
| COMP_KEY | 4 | 7.04 - 7.90 | The key used to invoke the current completion function. | Text | bash |
| COMP_LINE | 4 | 7.04 - 7.90 | The current command line. | Text | bash |
| COMP_POINT | 4 | 7.04 - 7.90 | The index of the cursor position relative to the beginning of the current command. | Text | bash |
| COMP_TYPE | 4 | 7.04 - 7.90 | Set to an integer value corresponding to the type of completion attempt. | Text | bash |
| COMP_WORDBREAKS | 4 | 7.04 - 7.90 | Characters that Readline treats as word separators when performing word completion. | Text | bash |
| COMP_WORDS | 4 | 7.04 - 7.90 | An array of the individual words in the current command line. | Text | bash |
| CONSOLE | The console tty used by this Shell. | ||||
| console (linenv) | The console tty used by this Shell. | ||||
| CONTENT_TYPE (linenv) | Decoded MIME Content-Type for reformime, defaults to 'text/plain'. | ||||
| COPROC | 4 | 7.04 - 7.90 | An array of file descriptors for I/O of an unnamed coprocess. | Text | bash |
| DATAFILE | TODO | ||||
| DEVNAME | TODO | ||||
| DEVPATH | The sysfs device path for mdev. | ||||
| DIRSTACK | 4 | 7.04 - 7.90 | An array of the current contents of the directory stack. | Text | bash |
| EDITOR (linenv) | The preferred text editor if set (ie: /usr/bin/nano). | ||||
| EMACS | 1 | 7.04 - 7.08 | Set if bash is running in an Emacs shell buffer to disable line editing. | Text | bash |
| ENCODING | Decoded MIME Content-Transfer-Encoding for reformime, defaults to '7bit'. | ||||
| ENV | Path to a profile script for ash. | ||||
| EUID | 4 | 7.04 - 7.90 | The numeric effective user id of the current user. | Text | bash |
| EXECIGNORE | 4 | 7.14 - 7.90 | Patterns of filenames to be ignored by command search using PATH. | Text | bash |
| EXINIT | Variable to customize vi. | ||||
| FIGNORE | 4 | 7.04 - 7.90 | Suffixes to ignore when performing filename completion. | Text | bash |
| FILENAME | Delivery filename for popmaildir connect helper program or target filename for reformime helper. | ||||
| FIRMWARE | The firmware to load for mdev. | ||||
| freq_drift_ppm | TODO | ||||
| FSCK_FORCE_ALL_PARALLEL | TODO | ||||
| FSCK_MAX_INST | TODO | ||||
| FSTAB_FILE | TODO | ||||
| FUNCNAME | 4 | 7.04 - 7.90 | Array of names of all shell functions currently in the execution call stack. | Text | bash |
| FUNCNEST | 4 | 7.04 - 7.90 | The maximum function nesting level. 0 = no limit. | Text | bash |
| GETCONF_DIR | 4 | 7.04 - 7.90 | Optional directory where getconf is located to query system variables. | Text | glibc |
| GETOPT_COMPATIBLE | Compatiblity tweak for getopt. | ||||
| GID | The group id of the user who owns this Shell. | ||||
| GLOBIGNORE | 4 | 7.04 - 7.90 | Patterns defining the set of filenames to be ignored by filename expansion. | Text | bash |
| GROUPS | 4 | 7.04 - 7.90 | An array of groups of which the current user is a member. | Text | bash |
| histchars | 4 | 7.04 - 7.90 | Up to 3 chars which control history expansion, quick substitution, and tokenization. | Text | bash |
| HISTCMD | 4 | 7.04 - 7.90 | The history number, or index in the history list, of the current command. | Text | bash |
| HISTCONTROL | 4 | 7.04 - 7.90 | List of values controlling how commands are saved on the history list. | Text | bash |
| HISTFILE | 4 | 7.04 - 7.90 | The name of the file to which the command history is saved. | Text | bash |
| HISTFILESIZE | 4 | 7.04 - 7.90 | The maximum number of lines contained in the history file. | Text | bash |
| HISTIGNORE | 4 | 7.04 - 7.90 | List of patterns masking command lines which should be saved on the history list. | Text | bash |
| HISTSIZE | 4 | 7.04 - 7.90 | The maximum number of commands to remember on the history list. | Text | bash |
| HISTTIMEFORMAT | 4 | 7.04 - 7.90 | Optional format string for the time displayed by the history builtin. | Text | bash |
| HOME (linenv) | 122 | 3.96 - 8.00 | The home directory of this Shell. | Text | uClibc, glibc, bash, musl |
| HOSTFILE | 4 | 7.04 - 7.90 | A file in the same format as '/etc/hosts' for hostname completion. | Text | bash |
| HOSTNAME | 4 | 7.04 - 7.90 | The hostname of this machine. | Text | bash |
| hostname_completion_file | 4 | 7.04 - 7.90 | Old name of the HOSTFILE variable. | Text | bash |
| HOSTTYPE | 4 | 7.04 - 7.90 | A string describing the machine Bash is running on. | Text | bash |
| HUSH_VERSION | TODO | ||||
| IFS | 11 | 7.04 - 8.00 | The character used as the internal field separator. | Text | glibc, bash |
| IGNOREEOF | 4 | 7.04 - 7.90 | Controls the action of the shell on receipt of an 'EOF' character. | Text | bash |
| ignoreeof | 4 | 7.04 - 7.90 | Controls the action of the shell on receipt of an 'EOF' character. | Text | bash |
| INSIDE_EMACS | 4 | 7.14 - 7.90 | Emacs 'version,comint' if bash is running inside an Emacs subshell. | Text | bash |
| interface (linenv) | TODO | ||||
| LANG | 133 | 4.61 - 8.00 | The language of this Shell to select the Locale. | Text | uClibc, glibc, bash, musl |
| LC_ALL | 133 | 4.61 - 8.00 | Forced Locale of this Shell for applications. | Text | uClibc, glibc, bash, musl |
| LC_COLLATE | 4 | 7.04 - 7.90 | The collation order used when sorting the results of filename expansion. | Text | bash |
| LC_CTYPE | 36 | 7.04 - 8.00 | The character set used to display and input text. | Text | glibc, bash, musl |
| LC_MESSAGES | 4 | 7.04 - 7.90 | The Locale used to translate double-quoted strings preceded by a '$'. | Text | bash |
| LC_NUMERIC | 4 | 7.04 - 7.90 | The Locale used for number formatting. | Text | bash |
| LC_TIME | 4 | 7.04 - 7.90 | The Locale used for date and time formatting. | Text | bash |
| LD_BIND_NOW | 30 | 7.19 - 8.00 | Causes the dynamic linker to resolve all symbols at program startup. | Text | uClibc |
| LD_LIBRARY_PATH | 25 | 7.19 - 8.00 | List of directories to search for Shared-Libraries before the standard locations. | Text | musl |
| LD_PRELOAD | 25 | 7.19 - 8.00 | List of objects which should be preloaded by the dynamic linker. | Text | musl |
| LINES | 4 | 7.04 - 7.90 | The number of text lines on the console window. | Text | bash |
| LOGIN_GID | TODO | ||||
| LOGIN_PRE_SUID_SCRIPT | TODO | ||||
| LOGIN_SHELL | TODO | ||||
| LOGIN_TIMEOUT | TODO | ||||
| LOGIN_TTY | TODO | ||||
| LOGIN_UID | TODO | ||||
| LOGIN_USER | TODO | ||||
| LOGNAME | 153 | 1.63 - 8.00 | Similar to USER, some programs prefer to read this variable. | Text | uClibc, musl |
| LS_COLORS | Colours to use for ls --color. | ||||
| MACHTYPE | 4 | 7.04 - 7.90 | Describes the system type on which Bash is executing, in the standard GNU format. | Text | bash |
| 4 | 7.04 - 7.90 | Optional filename or directory name to poll for mail. | Text | bash | |
| MAILCHECK | 4 | 7.04 - 7.90 | How often (in seconds) that the shell should check for mail. | Text | bash |
| MAILPATH | 4 | 7.04 - 7.90 | A list of filenames which the shell periodically checks for new mail. | Text | bash |
| MANDATORY_MANPATH | TODO | ||||
| MANPAGER | TODO | ||||
| MAPFILE | 4 | 7.04 - 7.90 | An array to hold the text read by the mapfile builtin. | Text | bash |
| offset | Offset of a busybox ntpd sync. | ||||
| OLDPWD (linenv) | 4 | 7.04 - 7.90 | The previous working directory of this Shell. | Text | bash |
| OPTARG | 4 | 7.04 - 7.90 | The value of the last option argument processed by the getopts builtin. | Text | bash |
| OPTERR | 4 | 7.04 - 7.90 | 1= Display error messages generated by builtin getopts. | Text | bash |
| OPTIND | 4 | 7.04 - 7.90 | The index of the last option argument processed by the getopts builtin. | Text | bash |
| OSTYPE | 4 | 7.04 - 7.90 | A string describing the operating system Bash is running on. | Text | bash |
| PAGER (linenv) | The preferred pager if set (ie: /usr/bin/less). | ||||
| PATH (linenv) | 141 | 1.63 - 8.00 | The path to search for commands of this Shell. | Text | uClibc, glibc |
| PATH_INFO (linenv) | TODO | ||||
| PIPESTATUS | 4 | 7.04 - 7.90 | An array of exit status values from most recent foreground pipeline. | Text | bash |
| poll_interval | TODO | ||||
| POSIXLY_CORRECT | 145 | 1.63 - 8.00 | If present: Try to behave according to the POSIX standard. | Text | uClibc, glibc, bash |
| POSIX_PEDANTIC | 4 | 7.04 - 7.90 | If present: Try to behave according to the POSIX standard. | Text | bash |
| PPID | 4 | 7.04 - 7.90 | The process ID of the shell's parent process. | Text | bash |
| PRINTER | TODO | ||||
| PROMPT_COMMAND | 4 | 7.04 - 7.90 | Optional command to execute before the printing of each primary prompt (PS1). | Text | bash |
| PROMPT_DIRTRIM | 4 | 7.04 - 7.90 | Optional number of directory components when expanding the 'w' and 'W' prompt string escapes | Text | bash |
| PROTO (linenv) | TODO | ||||
| PS0 | 4 | 7.14 - 7.90 | Prompt for interactive shells printed between reading and executing a command. | Text | bash |
| PS1 | 5 | 1.63 - 7.90 | The primary prompt string. | Text | busybox, bash |
| PS2 | 5 | 1.63 - 7.90 | The secondary prompt string. | Text | busybox, bash |
| PS3 | 4 | 7.04 - 7.90 | Optional prompt for the select command. | Text | bash |
| PS4 | 4 | 7.04 - 7.90 | The prompt printed before the command line is echoed when the '-x' option is set. | Text | bash |
| PWD (linenv) | 162 | 1.63 - 8.00 | The current working directory of this Shell. | Text | uClibc, glibc, musl |
| QUERY_STRING | TODO | ||||
| RANDOM | 3 | 7.04 - 7.51 | Generates a random integer (0 - 32767) each time this parameter is referenced. | Text | bash |
| READLINE_LINE | 4 | 7.04 - 7.90 | The contents of the Readline line buffer, for use with 'bind -x'. | Text | bash |
| READLINE_POINT | 4 | 7.04 - 7.90 | The position of the insertion point in the Readline line buffer, for use with 'bind -x'. | Text | bash |
| REMOTE_ADDR (linenv) | TODO | ||||
| REMOTE_PORT (linenv) | TODO | ||||
| REMOTE_USER | TODO | ||||
| REPLY | The default variable for the read builtin. | ||||
| REQUEST_METHOD (linenv) | TODO | ||||
| REQUEST_URI | TODO | ||||
| RLENGTH | Stores the length of the search string/pattern for awk. | ||||
| RSTART | Stores the starting location of the search string/pattern for awk. | ||||
| RUNLEVEL (linenv) | The current system runlevel. | ||||
| SCRIPT_FILENAME | TODO | ||||
| SCRIPT_NAME (linenv) | TODO | ||||
| SECONDS | 3 | 7.04 - 7.51 | The number of seconds since the shell was started. | Text | bash |
| SEQNUM | The sequence number for mdev. | ||||
| SHELL (linenv) | The absolute path of this Shell. | ||||
| SHELLOPTS | 4 | 7.04 - 7.90 | A colon-separated list of enabled shell options maintained by the set builtin. | Text | bash |
| SHLVL (linenv) | 4 | 7.04 - 7.90 | The number of shell levels running above this Shell. | Text | bash |
| SMTPHOST | TODO | ||||
| stratum | TODO | ||||
| SUBSYSTEM | The sybsystem to use for mdev. | ||||
| SUSHELL | TODO | ||||
| sushell | TODO | ||||
| SVDIR | Overrides the services directory /var/service (for sv/runsv). | ||||
| SVWAIT | Overrides the 7s to wait for a command to run (for sv/runsv). | ||||
| TCPCONCURRENCY (linenv) | TODO | ||||
| TCPORIGDSTADDR | TODO | ||||
| TERM (linenv) | The terminal emulation used by this Shell. | ||||
| TERMCAP | 4 | 7.04 - 7.90 | Termcap description, set by a terminal emulator to provide the terminal's characteristics. | Text | bash |
| TEXTDOMAIN | 4 | 7.04 - 7.90 | The name of the current Locale. | Text | bash |
| TEXTDOMAINDIR | 4 | 7.04 - 7.90 | The absolute pathname of the directory storing Locales. | Text | bash |
| TIME | Optional default format for busybox time (-v,-p,-f override this). | ||||
| TMOUT | 4 | 7.04 - 7.90 | Optional default timeout for the read builtin. 0 = no timeout. | Text | bash |
| TMPDIR | 11 | 7.04 - 8.00 | Optional path where temporary files for the Shell are created. | Text | glibc, bash |
| TZ (linenv) | 4 | 7.04 - 7.90 | The time zone used by this Shell. | Text | bash |
| UID | The unique id of the user who owns this Shell. | ||||
| USER (linenv) | The user who owns this Shell. | ||||
| VISUAL | TODO | ||||
| 174 Linux variables | |||||
