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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/libc/gen/exec.3,v 1.5 2007/12/21 22:14:04 swildner 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.
76 manual page provides detailed information about the execution of
79 The initial argument for these functions is the pathname of a file which
84 and subsequent ellipses in the
89 functions can be thought of as
94 Together they describe a list of one or more pointers to null-terminated
95 strings that represent the argument list available to the executed program.
96 The first argument, by convention, should point to the file name associated
97 with the file being executed.
109 functions provide an array of pointers to null-terminated strings that
110 represent the argument list available to the new program.
111 The first argument, by convention, should point to the file name associated
112 with the file being executed.
113 The array of pointers
123 functions also specify the environment of the executed process by following
126 pointer that terminates the list of arguments in the argument list
127 or the pointer to the argv array with an additional argument.
128 This additional argument is an array of pointers to null-terminated strings
134 The other functions take the environment for the new process image from the
137 in the current process.
139 Some of these functions have special semantics.
145 will duplicate the actions of the shell in searching for an executable file
146 if the specified file name does not contain a slash
149 The search path is the path specified in the environment by
152 If this variable isn't specified,
153 the default path is set according to the
158 .Dq Ev /usr/bin:/bin .
159 In addition, certain errors are treated specially.
161 If an error is ambiguous (for simplicity, we shall consider all
164 as being ambiguous here, although only the critical error
166 is really ambiguous),
167 then these functions will act as if they stat the file to determine
168 whether the file exists and has suitable execute permissions.
169 If it does, they will return immediately with the global variable
171 restored to the value set by
173 Otherwise, the search will be continued.
174 If the search completes without performing a successful
176 or terminating due to an error,
177 these functions will return with the global variable
183 according to whether at least one file with suitable execute permissions
186 If the header of a file isn't recognized (the attempted
190 these functions will execute the shell with the path of
191 the file as its first argument.
192 (If this attempt fails, no further searching is done.)
196 executes a file with the program tracing facilities enabled (see
201 functions returns, an error will have occurred.
202 The return value is \-1, and the global variable
204 will be set to indicate the error.
206 .Bl -tag -width /bin/sh -compact
211 Historically, the default path for the
216 .Dq Pa :/bin:/usr/bin .
217 This was changed to place the current directory last to enhance system
224 when errors occur while attempting to execute the file is not quite historic
225 practice, and has not traditionally been documented and is not specified
230 Traditionally, the functions
234 ignored all errors except for the ones described above and
236 upon which they retried after sleeping for several seconds, and
240 upon which they returned.
243 and determine existence and executability more carefully.
246 for inaccessible directories in the path prefix is no longer
249 for files with unsuitable execute permissions.
252 they returned upon all errors except
258 This was inferior to the traditional error handling,
259 since it breaks the ignoring of errors for path prefixes
260 and only improves the handling of the unusual ambiguous error
262 and the unusual error
264 The behaviour was changed to match the behaviour of
276 for any of the errors specified for the library functions
288 for any of the errors specified for the library function