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28 .\" @(#)execve.2 8.5 (Berkeley) 6/1/94
29 .\" $FreeBSD: src/lib/libc/sys/execve.2,v 1.16.2.10 2001/12/22 01:21:30 jwd Exp $
42 .Fn execve "const char *path" "char *const argv[]" "char *const envp[]"
45 transforms the calling process into a new process.
46 The new process is constructed from an ordinary file,
47 whose name is pointed to by
50 .Em new process file .
51 This file is either an executable object file,
52 or a file of data for an interpreter.
53 An executable object file consists of an identifying header,
54 followed by pages of data representing the initial program (text)
55 and initialized data pages. Additional pages may be specified
56 by the header to be initialized with zero data; see
61 An interpreter file begins with a line of the form:
63 .Bd -ragged -offset indent -compact
69 When an interpreter file is
77 is specified, it becomes the first argument to the
79 and the name of the originally
81 file becomes the second argument;
82 otherwise, the name of the originally
84 file becomes the first argument. The original arguments are shifted over to
85 become the subsequent arguments.
86 The zeroth argument is set to the specified
90 for a detailed discussion of interpreter file execution.)
94 is a pointer to a null-terminated array of
95 character pointers to null-terminated character strings.
96 These strings construct the argument list to be made available to the new
97 process. At least one argument must be present in
98 the array; by custom, the first element should be
99 the name of the executed program (for example, the last component of
104 is also a pointer to a null-terminated array of
105 character pointers to null-terminated strings.
106 A pointer to this array is normally stored in the global variable
108 These strings pass information to the
109 new process that is not directly an argument to the command (see
112 File descriptors open in the calling process image remain open in
113 the new process image, except for those for which the close-on-exec
118 Descriptors that remain open are unaffected by
121 Signals set to be ignored in the calling process are set to be ignored in
124 Signals which are set to be caught in the calling process image
125 are set to default action in the new process image.
126 Blocked signals remain blocked regardless of changes to the signal action.
127 The signal stack is reset to be undefined (see
129 for more information).
131 If the set-user-ID mode bit of the new process image file is set
134 the effective user ID of the new process image is set to the owner ID
135 of the new process image file.
136 If the set-group-ID mode bit of the new process image file is set,
137 the effective group ID of the new process image is set to the group ID
138 of the new process image file.
139 (The effective group ID is the first element of the group list.)
140 The real user ID, real group ID and
141 other group IDs of the new process image remain the same as the calling
143 After any set-user-ID and set-group-ID processing,
144 the effective user ID is recorded as the saved set-user-ID,
145 and the effective group ID is recorded as the saved set-group-ID.
146 These values may be used in changing the effective IDs later (see
149 The set-ID bits are not honored if the respective file system has the
151 option enabled or if the new process file is an interpreter file. Syscall
152 tracing is disabled if effective IDs are changed.
154 The new process also inherits the following attributes from
157 .Bl -column parent_process_ID -offset indent -compact
158 .It process ID Ta see Xr getpid 2
159 .It parent process ID Ta see Xr getppid 2
160 .It process group ID Ta see Xr getpgrp 2
161 .It access groups Ta see Xr getgroups 2
162 .It working directory Ta see Xr chdir 2
163 .It root directory Ta see Xr chroot 2
164 .It control terminal Ta see Xr termios 4
165 .It resource usages Ta see Xr getrusage 2
166 .It interval timers Ta see Xr getitimer 2
167 .It resource limits Ta see Xr getrlimit 2
168 .It file mode mask Ta see Xr umask 2
169 .It signal mask Ta see Xr sigaction 2 ,
173 When a program is executed as a result of an
175 call, it is entered as follows:
176 .Bd -literal -offset indent
177 main(argc, argv, envp)
184 is the number of elements in
189 points to the array of character pointers
190 to the arguments themselves.
194 function overlays the current process image
195 with a new process image the successful call
196 has no process to return to.
199 does return to the calling process an error has occurred; the
200 return value will be -1 and the global variable
202 is set to indicate the error.
205 will fail and return to the calling process if:
208 A component of the path prefix is not a directory.
209 .It Bq Er ENAMETOOLONG
210 A component of a pathname exceeded 255 characters,
211 or an entire path name exceeded 1023 characters.
212 .It Bq Er ENAMETOOLONG
213 When invoking an interpreted script, the interpreter name
218 The new process file does not exist.
220 Too many symbolic links were encountered in translating the pathname.
222 Search permission is denied for a component of the path prefix.
224 The new process file is not an ordinary file.
226 The new process file mode denies execute permission.
228 The new process file has the appropriate access
229 permission, but has an invalid magic number in its header.
231 The new process file is a pure procedure (shared text)
232 file that is currently open for writing or reading by some process.
234 The new process requires more virtual memory than
235 is allowed by the imposed maximum
238 The number of bytes in the new process' argument list
239 is larger than the system-imposed limit.
240 This limit is specified by the
245 The new process file is not as long as indicated by
246 the size values in its header.
253 to an illegal address.
255 An I/O error occurred while reading from the file system.
260 to a non-super-user, but is executed when
263 is ``root'', then the program has some of the powers
264 of a super-user as well.
280 function call appeared in