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32 .\" @(#)exec.3 6.4 (Berkeley) 4/19/91
34 .\" Converted for Linux, Mon Nov 29 11:12:48 1993, faith@cs.unc.edu
35 .\" Updated more for Linux, Tue Jul 15 11:54:18 1997, pacman@cqc.com
36 .\" Modified, 24 Jun 2004, Michael Kerrisk <mtk-manpages@gmx.net>
37 .\" Added note on casting NULL
39 .TH EXEC 3 1993-11-29 "GNU" "Linux Programmer's Manual"
41 execl, execlp, execle, execv, execvp \- execute a file
43 .B #include <unistd.h>
45 .B extern char **environ;
47 .BI "int execl(const char *" path ", const char *" arg ", ...);"
49 .BI "int execlp(const char *" file ", const char *" arg ", ...);"
51 .BI "int execle(const char *" path ", const char *" arg ,
53 .BI " ..., char * const " envp "[]);"
55 .BI "int execv(const char *" path ", char *const " argv "[]);"
57 .BI "int execvp(const char *" file ", char *const " argv "[]);"
61 family of functions replaces the current process image with a new process
63 The functions described in this manual page are front-ends for the
66 (See the manual page for
68 for detailed information about the replacement of the current process.)
70 The initial argument for these functions is the pathname of a file which is
75 and subsequent ellipses in the
80 functions can be thought of as
85 Together they describe a list of one or more pointers to null-terminated
86 strings that represent the argument list available to the executed program.
87 The first argument, by convention, should point to the filename associated
88 with the file being executed.
91 be terminated by a NULL
92 pointer, and, since these are variadic functions, this pointer must be cast
99 functions provide an array of pointers to null-terminated strings that
100 represent the argument list available to the new program.
101 The first argument, by convention, should point to the filename
102 associated with the file being executed.
103 The array of pointers
105 be terminated by a NULL pointer.
109 function also specifies the environment of the executed process by following
111 pointer that terminates the list of arguments in the parameter list or the
112 pointer to the argv array with an additional parameter.
114 parameter is an array of pointers to null-terminated strings and
116 be terminated by a NULL pointer.
117 The other functions take the environment for the new process
118 image from the external variable
120 in the current process.
121 .SS Special semantics for execlp() and execvp()
127 will duplicate the actions of the shell in searching for an executable file
128 if the specified filename does not contain a slash (/) character.
129 The search path is the path specified in the environment by the
132 If this variable isn't specified, the default path
133 ``:/bin:/usr/bin'' is used.
135 errors are treated specially.
137 If permission is denied for a file (the attempted
141 these functions will continue searching the rest of the search path.
142 If no other file is found, however,
143 they will return with the global variable
148 If the header of a file isn't recognized (the attempted
152 these functions will execute the shell
154 with the path of the file as its first argument.
155 (If this attempt fails, no further searching is done.)
159 functions returns, an error will have occurred.
160 The return value is \-1,
161 and the global variable
163 will be set to indicate the error.
165 All of these functions may fail and set
167 for any of the errors specified for the library function
172 On some other systems the default path (used when the environment
173 does not contain the variable \fBPATH\fR) has the current working
174 directory listed after
178 as an anti-Trojan-horse measure.
180 traditional "current directory first" default path.
186 when errors occur while attempting to execute the file is historic
187 practice, but has not traditionally been documented and is not specified by
189 BSD (and possibly other systems) do an automatic
193 Linux treats it as a hard
194 error and returns immediately.
196 Traditionally, the functions
200 ignored all errors except for the ones described above and
204 upon which they returned.
205 They now return if any error other than the ones
206 described above occurs.