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32 .\" @(#)exec.3 8.3 (Berkeley) 1/24/94
33 .\" $FreeBSD: src/lib/libc/gen/exec.3,v 1.7.2.8 2003/03/15 15:11:05 trhodes Exp $
34 .\" $DragonFly: src/lib/libcr/gen/Attic/exec.3,v 1.2 2003/06/17 04:26:42 dillon Exp $
51 .Vt extern char **environ ;
53 .Fn execl "const char *path" "const char *arg" ...
55 .Fn execlp "const char *file" "const char *arg" ...
57 .Fn execle "const char *path" "const char *arg" ...
59 .Fn exect "const char *path" "char *const argv[]" "char *const envp[]"
61 .Fn execv "const char *path" "char *const argv[]"
63 .Fn execvp "const char *file" "char *const argv[]"
67 family of functions replaces the current process image with a
69 The functions described in this manual page are front-ends for the function
71 (See the manual page for
73 for detailed information about the replacement of the current process.)
75 The initial argument for these functions is the pathname of a file which
80 and subsequent ellipses in the
85 functions can be thought of as
90 Together they describe a list of one or more pointers to null-terminated
91 strings that represent the argument list available to the executed program.
92 The first argument, by convention, should point to the file name associated
93 with the file being executed.
105 functions provide an array of pointers to null-terminated strings that
106 represent the argument list available to the new program.
107 The first argument, by convention, should point to the file name associated
108 with the file being executed.
109 The array of pointers
119 functions also specify the environment of the executed process by following
122 pointer that terminates the list of arguments in the argument list
123 or the pointer to the argv array with an additional argument.
124 This additional argument is an array of pointers to null-terminated strings
130 The other functions take the environment for the new process image from the
133 in the current process.
135 Some of these functions have special semantics.
141 will duplicate the actions of the shell in searching for an executable file
142 if the specified file name does not contain a slash
145 The search path is the path specified in the environment by
148 If this variable isn't specified,
149 the default path is set according to the
154 .Dq Ev /usr/bin:/bin .
155 In addition, certain errors are treated specially.
157 If an error is ambiguous (for simplicity, we shall consider all
160 as being ambiguous here, although only the critical error
162 is really ambiguous),
163 then these functions will act as if they stat the file to determine
164 whether the file exists and has suitable execute permissions.
165 If it does, they will return immediately with the global variable
167 restored to the value set by
169 Otherwise, the search will be continued.
170 If the search completes without performing a successful
172 or terminating due to an error,
173 these functions will return with the global variable
179 according to whether at least one file with suitable execute permissions
182 If the header of a file isn't recognized (the attempted
186 these functions will execute the shell with the path of
187 the file as its first argument.
188 (If this attempt fails, no further searching is done.)
192 executes a file with the program tracing facilities enabled (see
197 functions returns, an error will have occurred.
198 The return value is \-1, and the global variable
200 will be set to indicate the error.
202 .Bl -tag -width /bin/sh -compact
216 for any of the errors specified for the library functions
228 for any of the errors specified for the library function
238 Historically, the default path for the
243 .Dq Pa :/bin:/usr/bin .
244 This was changed to place the current directory last to enhance system
251 when errors occur while attempting to execute the file is not quite historic
252 practice, and has not traditionally been documented and is not specified
257 Traditionally, the functions
261 ignored all errors except for the ones described above and
263 upon which they retried after sleeping for several seconds, and
267 upon which they returned.
270 and determine existence and executability more carefully.
273 for inaccessible directories in the path prefix is no longer
276 for files with unsuitable execute permissions.
279 they returned upon all errors except
285 This was inferior to the traditional error handling,
286 since it breaks the ignoring of errors for path prefixes
287 and only improves the handling of the unusual ambiguous error
289 and the unusual error
291 The behaviour was changed to match the behaviour of