1EXEC(3) Linux Programmer's Manual EXEC(3)
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6 execl, execlp, execle, execv, execvp - execute a file
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9 #include <unistd.h>
10 extern char **environ;
12 int execl(const char *path, const char *arg, ...);
14 int execlp(const char *file, const char *arg, ...);
15 int execle(const char *path, const char *arg,
16 ..., char * const envp[]);
17 int execv(const char *path, char *const argv[]);
18 int execvp(const char *file, char *const argv[]);
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21 The exec() family of functions replaces the current process image with
22 a new process image. The functions described in this manual page are
23 front-ends for the function execve(2). (See the manual page for
24 execve() for detailed information about the replacement of the current
25 process.)
26 The initial argument for these functions is the pathname of a file
28 which is to be executed.
29 The const char *arg and subsequent ellipses in the execl(), execlp(),
31 and execle() functions can be thought of as arg0, arg1, ..., argn.
32 Together they describe a list of one or more pointers to null-termi‐
33 nated strings that represent the argument list available to the exe‐
34 cuted program. The first argument, by convention, should point to the
35 filename associated with the file being executed. The list of argu‐
36 ments must be terminated by a NULL pointer, and, since these are vari‐
37 adic functions, this pointer must be cast (char *) NULL.
38 The execv() and execvp() functions provide an array of pointers to
40 null-terminated strings that represent the argument list available to
41 the new program. The first argument, by convention, should point to
42 the filename associated with the file being executed. The array of
43 pointers must be terminated by a NULL pointer.
44 The execle() function also specifies the environment of the executed
46 process by following the NULL pointer that terminates the list of argu‐
47 ments in the parameter list or the pointer to the argv array with an
48 additional parameter. This additional parameter is an array of point‐
49 ers to null-terminated strings and must be terminated by a NULL
50 pointer. The other functions take the environment for the new process
51 image from the external variable environ in the current process.
52 Some of these functions have special semantics.
54 The functions execlp() and execvp() will duplicate the actions of the
56 shell in searching for an executable file if the specified filename
57 does not contain a slash (/) character. The search path is the path
58 specified in the environment by the PATH variable. If this variable
59 isn't specified, the default path ``:/bin:/usr/bin'' is used. In addi‐
60 tion, certain errors are treated specially.
61 If permission is denied for a file (the attempted execve() returned
63 EACCES), these functions will continue searching the rest of the search
64 path. If no other file is found, however, they will return with the
65 global variable errno set to EACCES.
66 If the header of a file isn't recognized (the attempted execve()
68 returned ENOEXEC), these functions will execute the shell with the path
69 of the file as its first argument. (If this attempt fails, no further
70 searching is done.)
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73 If any of the exec() functions returns, an error will have occurred.
74 The return value is -1, and the global variable errno will be set to
75 indicate the error.
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78 /bin/sh
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81 All of these functions may fail and set errno for any of the errors
82 specified for the library function execve(2).
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85 sh(1), execve(2), fork(2), ptrace(2), fexecve(3), environ(7)
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88 On some other systems the default path (used when the environment does
89 not contain the variable PATH) has the current working directory listed
90 after /bin and /usr/bin, as an anti-Trojan-horse measure. Linux uses
91 here the traditional "current directory first" default path.
92 The behavior of execlp() and execvp() when errors occur while attempt‐
94 ing to execute the file is historic practice, but has not traditionally
95 been documented and is not specified by the POSIX standard. BSD (and
96 possibly other systems) do an automatic sleep and retry if ETXTBSY is
97 encountered. Linux treats it as a hard error and returns immediately.
98 Traditionally, the functions execlp() and execvp() ignored all errors
100 except for the ones described above and ENOMEM and E2BIG, upon which
101 they returned. They now return if any error other than the ones
102 described above occurs.
103
105 POSIX.1-2001.
106BSD MANPAGE 1993-11-29 EXEC(3)