Emacs provides access to variables in the operating system environment through various functions. These variables include the name of the system, the user’s UID, and so on.
This variable holds the standard GNU configuration name for the hardware/software configuration of your system, as a string. For example, a typical value for a 64-bit GNU/Linux system is ‘"x86_64-unknown-linux-gnu"’.
The value of this variable is a symbol indicating the type of operating system Emacs is running on. The possible values are:
Berkeley BSD and its variants.
Cygwin, a POSIX layer on top of MS-Windows.
The GNU system (using the GNU kernel, which consists of the HURD and Mach).
A GNU/Linux system—that is, a variant GNU system, using the Linux kernel. (These systems are the ones people often call “Linux”, but actually Linux is just the kernel, not the whole system.)
A GNU (glibc-based) system with a FreeBSD kernel.
Hewlett-Packard HPUX operating system.
Google Native Client (NaCl) sandboxing system.
Microsoft’s DOS. Emacs compiled with DJGPP for MS-DOS binds
ms-dos even when you run it on MS-Windows.
AT&T Unix System V.
Microsoft Windows NT, 9X and later. The value of
windows-nt, e.g., even on Windows 10.
We do not wish to add new symbols to make finer distinctions unless it
is absolutely necessary! In fact, we hope to eliminate some of these
alternatives in the future. If you need to make a finer distinction
system-type allows for, you can test
system-configuration, e.g., against a regexp.
This function returns the name of the machine you are running on, as a string.
If this variable is non-
nil, it is used instead of
system-name for purposes of generating email addresses. For
example, it is used when constructing the default value of
user-mail-address. See User Identification.
This function returns the value of the environment variable var,
as a string. var should be a string. If var is undefined
in the environment,
nil. It returns
‘""’ if var is set but null. Within Emacs, a list of environment
variables and their values is kept in the variable
(getenv "USER") ⇒ "lewis"
The shell command
printenv prints all or part of the environment:
bash$ printenv PATH=/usr/local/bin:/usr/bin:/bin USER=lewis
TERM=xterm SHELL=/bin/bash HOME=/home/lewis
This command sets the value of the environment variable named
variable to value. variable should be a string.
Internally, Emacs Lisp can handle any string. However, normally
variable should be a valid shell identifier, that is, a sequence
of letters, digits and underscores, starting with a letter or
underscore. Otherwise, errors may occur if subprocesses of Emacs try
to access the value of variable. If value is omitted or
nil (or, interactively, with a prefix argument),
removes variable from the environment. Otherwise, value
should be a string.
If the optional argument substitute is non-
calls the function
substitute-env-vars to expand any
environment variables in value.
setenv works by modifying
that variable with
let is also reasonable practice.
setenv returns the new value of variable, or
if it removed variable from the environment.
This variable is a list of strings, each describing one environment
variable. The functions
setenv work by means
of this variable.
process-environment ⇒ ("PATH=/usr/local/bin:/usr/bin:/bin" "USER=lewis"
"TERM=xterm" "SHELL=/bin/bash" "HOME=/home/lewis" …)
process-environment contains multiple elements that
specify the same environment variable, the first of these elements
specifies the variable, and the others are ignored.
This variable holds the list of environment variables Emacs inherited from its parent process when Emacs started.
This variable holds a string that says which character separates
directories in a search path (as found in an environment variable). Its
":" for Unix and GNU systems, and
";" for MS systems.
This function takes a search path string such as the value of
PATH environment variable, and splits it at the separators,
returning a list of directories.
nil in this list means
the current directory. Although the function’s name says
“colon”, it actually uses the value of
(parse-colon-path ":/foo:/bar") ⇒ (nil "/foo/" "/bar/")
This variable holds the program name under which Emacs was invoked. The value is a string, and does not include a directory name.
This variable holds the directory in which the Emacs executable was
located when it was run, or
nil if that directory cannot be
nil, this is a directory within which to look for the
lib-src and etc subdirectories. In an installed Emacs,
it is normally
nil. It is non-
when Emacs can’t find those directories in their standard installed
locations, but can find them in a directory related somehow to the one
containing the Emacs executable (i.e.,
This function returns the current 1-minute, 5-minute, and 15-minute system load averages, in a list. The load average indicates the number of processes trying to run on the system.
By default, the values are integers that are 100 times the system load
averages, but if use-float is non-
nil, then they are
returned as floating-point numbers without multiplying by 100.
If it is impossible to obtain the load average, this function signals an error. On some platforms, access to load averages requires installing Emacs as setuid or setgid so that it can read kernel information, and that usually isn’t advisable.
If the 1-minute load average is available, but the 5- or 15-minute averages are not, this function returns a shortened list containing the available averages.
(load-average) ⇒ (169 48 36)
(load-average t) ⇒ (1.69 0.48 0.36)
The shell command
uptime returns similar information.
This function returns the process ID of the Emacs process, as an integer.
This variable holds the erase character that was selected in the system’s terminal driver, before Emacs was started.