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32 .\" @(#)execve.2 8.5 (Berkeley) 6/1/94
33 .\" $FreeBSD: src/lib/libc/sys/execve.2,v 1.16.2.10 2001/12/22 01:21:30 jwd Exp $
46 .Fn execve "const char *path" "char *const argv[]" "char *const envp[]"
49 transforms the calling process into a new process.
50 The new process is constructed from an ordinary file,
51 whose name is pointed to by
54 .Em new process file .
55 This file is either an executable object file,
56 or a file of data for an interpreter.
57 An executable object file consists of an identifying header,
58 followed by pages of data representing the initial program (text)
59 and initialized data pages. Additional pages may be specified
60 by the header to be initialized with zero data; see
65 An interpreter file begins with a line of the form:
67 .Bd -ragged -offset indent -compact
73 When an interpreter file is
81 is specified, it becomes the first argument to the
83 and the name of the originally
85 file becomes the second argument;
86 otherwise, the name of the originally
88 file becomes the first argument. The original arguments are shifted over to
89 become the subsequent arguments.
90 The zeroth argument is set to the specified
94 for a detailed discussion of interpreter file execution.)
98 is a pointer to a null-terminated array of
99 character pointers to null-terminated character strings.
100 These strings construct the argument list to be made available to the new
101 process. At least one argument must be present in
102 the array; by custom, the first element should be
103 the name of the executed program (for example, the last component of
108 is also a pointer to a null-terminated array of
109 character pointers to null-terminated strings.
110 A pointer to this array is normally stored in the global variable
112 These strings pass information to the
113 new process that is not directly an argument to the command (see
116 File descriptors open in the calling process image remain open in
117 the new process image, except for those for which the close-on-exec
122 Descriptors that remain open are unaffected by
125 Signals set to be ignored in the calling process are set to be ignored in
128 Signals which are set to be caught in the calling process image
129 are set to default action in the new process image.
130 Blocked signals remain blocked regardless of changes to the signal action.
131 The signal stack is reset to be undefined (see
133 for more information).
135 If the set-user-ID mode bit of the new process image file is set
138 the effective user ID of the new process image is set to the owner ID
139 of the new process image file.
140 If the set-group-ID mode bit of the new process image file is set,
141 the effective group ID of the new process image is set to the group ID
142 of the new process image file.
143 (The effective group ID is the first element of the group list.)
144 The real user ID, real group ID and
145 other group IDs of the new process image remain the same as the calling
147 After any set-user-ID and set-group-ID processing,
148 the effective user ID is recorded as the saved set-user-ID,
149 and the effective group ID is recorded as the saved set-group-ID.
150 These values may be used in changing the effective IDs later (see
153 The set-ID bits are not honored if the respective file system has the
155 option enabled or if the new process file is an interpreter file. Syscall
156 tracing is disabled if effective IDs are changed.
158 The new process also inherits the following attributes from
161 .Bl -column parent_process_ID -offset indent -compact
162 .It process ID Ta see Xr getpid 2
163 .It parent process ID Ta see Xr getppid 2
164 .It process group ID Ta see Xr getpgrp 2
165 .It access groups Ta see Xr getgroups 2
166 .It working directory Ta see Xr chdir 2
167 .It root directory Ta see Xr chroot 2
168 .It control terminal Ta see Xr termios 4
169 .It resource usages Ta see Xr getrusage 2
170 .It interval timers Ta see Xr getitimer 2
171 .It resource limits Ta see Xr getrlimit 2
172 .It file mode mask Ta see Xr umask 2
173 .It signal mask Ta see Xr sigaction 2 ,
177 When a program is executed as a result of an
179 call, it is entered as follows:
180 .Bd -literal -offset indent
181 main(argc, argv, envp)
188 is the number of elements in
193 points to the array of character pointers
194 to the arguments themselves.
198 function overlays the current process image
199 with a new process image the successful call
200 has no process to return to.
203 does return to the calling process an error has occurred; the
204 return value will be -1 and the global variable
206 is set to indicate the error.
209 will fail and return to the calling process if:
212 A component of the path prefix is not a directory.
213 .It Bq Er ENAMETOOLONG
214 A component of a pathname exceeded 255 characters,
215 or an entire path name exceeded 1023 characters.
216 .It Bq Er ENAMETOOLONG
217 When invoking an interpreted script, the interpreter name
222 The new process file does not exist.
224 Too many symbolic links were encountered in translating the pathname.
226 Search permission is denied for a component of the path prefix.
228 The new process file is not an ordinary file.
230 The new process file mode denies execute permission.
232 The new process file has the appropriate access
233 permission, but has an invalid magic number in its header.
235 The new process file is a pure procedure (shared text)
236 file that is currently open for writing or reading by some process.
238 The new process requires more virtual memory than
239 is allowed by the imposed maximum
242 The number of bytes in the new process' argument list
243 is larger than the system-imposed limit.
244 This limit is specified by the
249 The new process file is not as long as indicated by
250 the size values in its header.
257 to an illegal address.
259 An I/O error occurred while reading from the file system.
264 to a non-super-user, but is executed when
267 is ``root'', then the program has some of the powers
268 of a super-user as well.
284 function call appeared in