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28 .\" @(#)exec.3 8.3 (Berkeley) 1/24/94
47 .Vt extern char **environ ;
49 .Fn execl "const char *path" "const char *arg" ... /* "(char *)0" */
51 .Fn execlp "const char *file" "const char *arg" ... /* "(char *)0" */
54 .Fa "const char *path" "const char *arg" ...
57 .Fa "(char *)0" "char *const envp[]" */
61 .Fn exect "const char *path" "char *const argv[]" "char *const envp[]"
63 .Fn execv "const char *path" "char *const argv[]"
65 .Fn execvp "const char *file" "char *const argv[]"
67 .Fn execvP "const char *file" "const char *search_path" "char *const argv[]"
71 family of functions replaces the current process image with a
73 The functions described in this manual page are front-ends for the function
75 (See the manual page for
77 for detailed information about the replacement of the current process.)
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.
110 functions provide an array of pointers to null-terminated strings that
111 represent the argument list available to the new program.
112 The first argument, by convention, should point to the file name associated
113 with the file being executed.
114 The array of pointers
124 functions also specify the environment of the executed process by following
127 pointer that terminates the list of arguments in the argument list
128 or the pointer to the argv array with an additional argument.
129 This additional argument is an array of pointers to null-terminated strings
135 The other functions take the environment for the new process image from the
138 in the current process.
140 Some of these functions have special semantics.
147 will duplicate the actions of the shell in searching for an executable file
148 if the specified file name does not contain a slash
155 search path is the path specified in the environment by
158 If this variable is not specified,
159 the default path is set according to the
164 .Dq Ev /usr/bin:/bin .
167 the search path is specified as an argument to the function.
168 In addition, certain errors are treated specially.
170 If an error is ambiguous (for simplicity, we shall consider all
173 as being ambiguous here, although only the critical error
175 is really ambiguous),
176 then these functions will act as if they stat the file to determine
177 whether the file exists and has suitable execute permissions.
178 If it does, they will return immediately with the global variable
180 restored to the value set by
182 Otherwise, the search will be continued.
183 If the search completes without performing a successful
185 or terminating due to an error,
186 these functions will return with the global variable
192 according to whether at least one file with suitable execute permissions
195 If the header of a file is not recognized (the attempted
199 these functions will execute the shell with the path of
200 the file as its first argument.
201 (If this attempt fails, no further searching is done.)
205 executes a file with the program tracing facilities enabled (see
210 functions returns, an error will have occurred.
211 The return value is \-1, and the global variable
213 will be set to indicate the error.
215 .Bl -tag -width /bin/sh -compact
220 Historically, the default path for the
225 .Dq Pa :/bin:/usr/bin .
226 This was changed to remove the current directory to enhance system
233 when errors occur while attempting to execute the file is not quite historic
234 practice, and has not traditionally been documented and is not specified
239 Traditionally, the functions
243 ignored all errors except for the ones described above and
245 upon which they retried after sleeping for several seconds, and
249 upon which they returned.
252 and determine existence and executability more carefully.
255 for inaccessible directories in the path prefix is no longer
258 for files with unsuitable execute permissions.
261 they returned upon all errors except
267 This was inferior to the traditional error handling,
268 since it breaks the ignoring of errors for path prefixes
269 and only improves the handling of the unusual ambiguous error
271 and the unusual error
273 The behaviour was changed to match the behaviour of
286 for any of the errors specified for the library functions
298 for any of the errors specified for the library function
320 function first appeared in