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NAME |LIBRARY |SYNOPSIS |DESCRIPTION |RETURN VALUE |ERRORS |ATTRIBUTES |VERSIONS |STANDARDS |HISTORY |BUGS |SEE ALSO |COLOPHON | |
exec(3) Library Functions Manualexec(3)execl, execlp, execle, execv, execvp, execvpe - execute a file
Standard C library (libc,-lc)
#include <unistd.h>extern char **environ;int execl(const char *path, const char *arg, .../*, (char *) NULL */);int execlp(const char *file, const char *arg, .../*, (char *) NULL */);int execle(const char *path, const char *arg, .../*, (char *) NULL, char *constenvp[] */);int execv(const char *path, char *constargv[]);int execvp(const char *file, char *constargv[]);int execvpe(const char *file, char *constargv[], char *constenvp[]); Feature Test Macro Requirements for glibc (seefeature_test_macros(7)):execvpe(): _GNU_SOURCE
Theexec() family of functions replaces the current process image with a new process image. The functions described in this manual page are layered on top ofexecve(2). (See the manual page forexecve(2) for further details about the replacement of the current process image.) The initial argument for these functions is the name of a file that is to be executed. The functions can be grouped based on the letters following the "exec" prefix.l - execl(), execlp(), execle() Theconst char *arg and subsequent ellipses can be thought of asarg0,arg1, ...,argn. Together they describe a list of one or more pointers to null-terminated strings that represent the argument list available to the executed program. The first argument, by convention, should point to the filename associated with the file being executed. The list of argumentsmust be terminated by a null pointer, and, since these are variadic functions, this pointer must be cast(char *) NULL. By contrast with the 'l' functions, the 'v' functions (below) specify the command-line arguments of the executed program as a vector.v - execv(), execvp(), execvpe() Thechar *const argv[] argument is an array of pointers to null- terminated strings that represent the argument list available to the new program. The first argument, by convention, should point to the filename associated with the file being executed. The array of pointersmust be terminated by a null pointer.e - execle(), execvpe() The environment of the new process image is specified via the argumentenvp. Theenvp argument is an array of pointers to null- terminated strings andmust be terminated by a null pointer. All otherexec() functions (which do not include 'e' in the suffix) take the environment for the new process image from the external variableenviron in the calling process.p - execlp(), execvp(), execvpe() These functions duplicate the actions of the shell in searching for an executable file if the specified filename does not contain a slash (/) character. The file is sought in the colon-separated list of directory pathnames specified in thePATHenvironment variable. If this variable isn't defined, the path list defaults to a list that includes the directories returned byconfstr(_CS_PATH) (which typically returns the value "/bin:/usr/bin") and possibly also the current working directory; see VERSIONS for further details.execvpe() searches for the program using the value ofPATHfrom the caller's environment, not from theenvp argument. If the specified filename includes a slash character, thenPATHis ignored, and the file at the specified pathname is executed. In addition, certain errors are treated specially. If permission is denied for a file (the attemptedexecve(2) failed with the errorEACCES), these functions will continue searching the rest of the search path. If no other file is found, however, they will return witherrno set toEACCES. If the header of a file isn't recognized (the attemptedexecve(2) failed with the errorENOEXEC), these functions will execute the shell (/bin/sh) with the path of the file as its first argument. (If this attempt fails, no further searching is done.) All otherexec() functions (which do not include 'p' in the suffix) take as their first argument a (relative or absolute) pathname that identifies the program to be executed.
Theexec() functions return only if an error has occurred. The return value is -1, anderrno is set to indicate the error.
All of these functions may fail and seterrno for any of the errors specified forexecve(2).
For an explanation of the terms used in this section, seeattributes(7). ┌──────────────────────────────────┬───────────────┬─────────────┐ │Interface│Attribute│Value│ ├──────────────────────────────────┼───────────────┼─────────────┤ │execl(),execle(),execv() │ Thread safety │ MT-Safe │ ├──────────────────────────────────┼───────────────┼─────────────┤ │execlp(),execvp(),execvpe() │ Thread safety │ MT-Safe env │ └──────────────────────────────────┴───────────────┴─────────────┘
The default search path (used when the environment does not contain the variablePATH) shows some variation across systems. It generally includes/bin and/usr/bin (in that order) and may also include the current working directory. On some other systems, the current working is included after/bin and/usr/bin, as an anti-Trojan-horse measure. The glibc implementation long followed the traditional default where the current working directory is included at the start of the search path. However, some code refactoring during the development of glibc 2.24 caused the current working directory to be dropped altogether from the default search path. This accidental behavior change is considered mildly beneficial, and won't be reverted. The behavior ofexeclp() andexecvp() when errors occur while attempting to execute the file is historic practice, but has not traditionally been documented and is not specified by the POSIX standard. BSD (and possibly other systems) do an automatic sleep and retry ifETXTBSYis encountered. Linux treats it as a hard error and returns immediately. Traditionally, the functionsexeclp() andexecvp() ignored all errors except for the ones described above andENOMEMandE2BIG, upon which they returned. They now return if any error other than the ones described above occurs.
environexecl()execlp()execle()execv()execvp() POSIX.1-2008.execvpe() GNU.
environexecl()execlp()execle()execv()execvp() POSIX.1-2001.execvpe() glibc 2.11.
Before glibc 2.24,execl() andexecle() employedrealloc(3) internally and were consequently not async-signal-safe, in violation of the requirements of POSIX.1. This was fixed in glibc 2.24.Architecture-specific details On sparc and sparc64,execv() is provided as a system call by the kernel (with the prototype shown above) for compatibility with SunOS. This function isnot employed by theexecv() wrapper function on those architectures.
sh(1),execve(2),execveat(2),fork(2),ptrace(2),fexecve(3),system(3),environ(7)
This page is part of theman-pages (Linux kernel and C library user-space interface documentation) project. Information about the project can be found at ⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report for this manual page, see ⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩. This page was obtained from the tarball man-pages-6.15.tar.gz fetched from ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on 2025-08-11. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up- to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which isnot part of the original manual page), send a mail to man-pages@man7.orgLinux man-pages 6.15 2025-05-17exec(3)Pages that refer to this page:pmlogger(1), watch(1), xargs(1), execve(2), getpid(2), ptrace(2), seccomp(2), statfs(2), vfork(2), atexit(3), clearenv(3), confstr(3), glob(3), ibv_fork_init(3), libexpect(3), lttng-ust(3), on_exit(3), pam_getenvlist(3), posix_spawn(3), statvfs(3), stdin(3), sysconf(3), system(3), systemd.exec(5), environ(7), signal-safety(7)
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