Lisp programs sometimes need to run a shell and give it a command
that contains file names that were specified by the user. These
programs ought to be able to support any valid file name. But the shell
gives special treatment to certain characters, and if these characters
occur in the file name, they will confuse the shell. To handle these
characters, use the function
This function returns a string that represents, in shell syntax, an argument whose actual contents are argument. It should work reliably to concatenate the return value into a shell command and then pass it to a shell for execution.
Precisely what this function does depends on your operating system. The function is designed to work with the syntax of your system’s standard shell; if you use an unusual shell, you will need to redefine this function. See Security Considerations.
;; This example shows the behavior on GNU and Unix systems. (shell-quote-argument "foo > bar") ⇒ "foo\\ \\>\\ bar" ;; This example shows the behavior on MS-DOS and MS-Windows. (shell-quote-argument "foo > bar") ⇒ "\"foo > bar\""
Here’s an example of using
shell-quote-argument to construct
a shell command:
(concat "diff -u " (shell-quote-argument oldfile) " " (shell-quote-argument newfile))
The following two functions are useful for combining a list of
individual command-line argument strings into a single string, and
taking a string apart into a list of individual command-line
arguments. These functions are mainly intended for converting user
input in the minibuffer, a Lisp string, into a list of string
arguments to be passed to
start-process, or for converting such lists of arguments into a
single Lisp string to be presented in the minibuffer or echo area.
Note that if a shell is involved (e.g., if using
call-process-shell-command), arguments should still be
combine-and-quote-strings is not intended to protect
special characters from shell evaluation.
split-string-and-unquotestring &optional separators
This function splits string into substrings at matches for the
regular expression separators, like
(see Creating Strings); in addition, it removes quoting from the
substrings. It then makes a list of the substrings and returns it.
If separators is omitted or
nil, it defaults to
"\\s-+", which is a regular expression that matches one or more
characters with whitespace syntax (see Syntax Class Table).
This function supports two types of quoting: enclosing a whole string
in double quotes
"…", and quoting individual characters
with a backslash escape ‘\’. The latter is also used in Lisp
strings, so this function can handle those as well.
combine-and-quote-stringslist-of-strings &optional separator
This function concatenates list-of-strings into a single string,
quoting each string as necessary. It also sticks the separator
string between each pair of strings; if separator is omitted or
nil, it defaults to
" ". The return value is the
The strings in list-of-strings that need quoting are those that
include separator as their substring. Quoting a string encloses
it in double quotes
"…". In the simplest case, if you
are consing a command from the individual command-line arguments,
every argument that includes embedded blanks will be quoted.