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28 .\" @(#)exec.3 8.3 (Berkeley) 1/24/94
29 .\" $FreeBSD: src/lib/libc/gen/exec.3,v 1.28 2008/06/23 05:22:06 ed Exp $
30 .\" $DragonFly: src/lib/libc/gen/exec.3,v 1.5 2007/12/21 22:14:04 swildner Exp $
48 .Vt extern char **environ ;
50 .Fn execl "const char *path" "const char *arg" ...
52 .Fn execlp "const char *file" "const char *arg" ...
55 .Fa "const char *path" "const char *arg" ...
58 .Fn exect "const char *path" "char *const argv[]" "char *const envp[]"
60 .Fn execv "const char *path" "char *const argv[]"
62 .Fn execvp "const char *file" "char *const argv[]"
64 .Fn execvP "const char *file" "const char *search_path" "char *const argv[]"
68 family of functions replaces the current process image with a
70 The functions described in this manual page are front-ends for the function
72 (See the manual page for
74 for detailed information about the replacement of the current process.
77 manual page provides detailed information about the execution of
80 The initial argument for these functions is the pathname of a file which
85 and subsequent ellipses in the
90 functions can be thought of as
95 Together they describe a list of one or more pointers to null-terminated
96 strings that represent the argument list available to the executed program.
97 The first argument, by convention, should point to the file name associated
98 with the file being executed.
111 functions provide an array of pointers to null-terminated strings that
112 represent the argument list available to the new program.
113 The first argument, by convention, should point to the file name associated
114 with the file being executed.
115 The array of pointers
125 functions also specify the environment of the executed process by following
128 pointer that terminates the list of arguments in the argument list
129 or the pointer to the argv array with an additional argument.
130 This additional argument is an array of pointers to null-terminated strings
136 The other functions take the environment for the new process image from the
139 in the current process.
141 Some of these functions have special semantics.
148 will duplicate the actions of the shell in searching for an executable file
149 if the specified file name does not contain a slash
156 search path is the path specified in the environment by
159 If this variable is not specified,
160 the default path is set according to the
165 .Dq Ev /usr/bin:/bin .
168 the search path is specified as an argument to the function.
169 In addition, certain errors are treated specially.
171 If an error is ambiguous (for simplicity, we shall consider all
174 as being ambiguous here, although only the critical error
176 is really ambiguous),
177 then these functions will act as if they stat the file to determine
178 whether the file exists and has suitable execute permissions.
179 If it does, they will return immediately with the global variable
181 restored to the value set by
183 Otherwise, the search will be continued.
184 If the search completes without performing a successful
186 or terminating due to an error,
187 these functions will return with the global variable
193 according to whether at least one file with suitable execute permissions
196 If the header of a file is not recognized (the attempted
200 these functions will execute the shell with the path of
201 the file as its first argument.
202 (If this attempt fails, no further searching is done.)
206 executes a file with the program tracing facilities enabled (see
211 functions returns, an error will have occurred.
212 The return value is \-1, and the global variable
214 will be set to indicate the error.
216 .Bl -tag -width /bin/sh -compact
221 Historically, the default path for the
226 .Dq Pa :/bin:/usr/bin .
227 This was changed to place the current directory last to enhance system
234 when errors occur while attempting to execute the file is not quite historic
235 practice, and has not traditionally been documented and is not specified
240 Traditionally, the functions
244 ignored all errors except for the ones described above and
246 upon which they retried after sleeping for several seconds, and
250 upon which they returned.
253 and determine existence and executability more carefully.
256 for inaccessible directories in the path prefix is no longer
259 for files with unsuitable execute permissions.
262 they returned upon all errors except
268 This was inferior to the traditional error handling,
269 since it breaks the ignoring of errors for path prefixes
270 and only improves the handling of the unusual ambiguous error
272 and the unusual error
274 The behaviour was changed to match the behaviour of
287 for any of the errors specified for the library functions
299 for any of the errors specified for the library function
322 function first appeared in