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Diffstat (limited to 'lib/libc/gen/exec.3')
| -rw-r--r-- | lib/libc/gen/exec.3 | 321 |
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diff --git a/lib/libc/gen/exec.3 b/lib/libc/gen/exec.3 new file mode 100644 index 000000000000..daeccd10bf47 --- /dev/null +++ b/lib/libc/gen/exec.3 @@ -0,0 +1,321 @@ +.\" Copyright (c) 1991, 1993 +.\" The Regents of the University of California. All rights reserved. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" 4. Neither the name of the University nor the names of its contributors +.\" may be used to endorse or promote products derived from this software +.\" without specific prior written permission. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND +.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE +.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE +.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL +.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS +.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) +.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY +.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +.\" SUCH DAMAGE. +.\" +.\" @(#)exec.3 8.3 (Berkeley) 1/24/94 +.\" $FreeBSD$ +.\" +.Dd January 24, 1994 +.Dt EXEC 3 +.Os +.Sh NAME +.Nm execl , +.Nm execlp , +.Nm execle , +.Nm exect , +.Nm execv , +.Nm execvp , +.Nm execvP +.Nd execute a file +.Sh LIBRARY +.Lb libc +.Sh SYNOPSIS +.In unistd.h +.Vt extern char **environ ; +.Ft int +.Fn execl "const char *path" "const char *arg" ... /* "(char *)0" */ +.Ft int +.Fn execlp "const char *file" "const char *arg" ... /* "(char *)0" */ +.Ft int +.Fo execle +.Fa "const char *path" "const char *arg" ... +.Fa /* +.Bk -words +.Fa "(char *)0" "char *const envp[]" */ +.Ek +.Fc +.Ft int +.Fn exect "const char *path" "char *const argv[]" "char *const envp[]" +.Ft int +.Fn execv "const char *path" "char *const argv[]" +.Ft int +.Fn execvp "const char *file" "char *const argv[]" +.Ft int +.Fn execvP "const char *file" "const char *search_path" "char *const argv[]" +.Sh DESCRIPTION +The +.Nm exec +family of functions replaces the current process image with a +new process image. +The functions described in this manual page are front-ends for the function +.Xr execve 2 . +(See the manual page for +.Xr execve 2 +for detailed information about the replacement of the current process.) +.Pp +The initial argument for these functions is the pathname of a file which +is to be executed. +.Pp +The +.Fa "const char *arg" +and subsequent ellipses in the +.Fn execl , +.Fn execlp , +and +.Fn execle +functions can be thought of as +.Em arg0 , +.Em arg1 , +\&..., +.Em argn . +Together they describe a list of one or more pointers to null-terminated +strings that represent the argument list available to the executed program. +The first argument, by convention, should point to the file name associated +with the file being executed. +The list of arguments +.Em must +be terminated by a +.Dv NULL +pointer. +.Pp +The +.Fn exect , +.Fn execv , +.Fn execvp , +and +.Fn execvP +functions provide an array of pointers to null-terminated strings that +represent the argument list available to the new program. +The first argument, by convention, should point to the file name associated +with the file being executed. +The array of pointers +.Sy must +be terminated by a +.Dv NULL +pointer. +.Pp +The +.Fn execle +and +.Fn exect +functions also specify the environment of the executed process by following +the +.Dv NULL +pointer that terminates the list of arguments in the argument list +or the pointer to the argv array with an additional argument. +This additional argument is an array of pointers to null-terminated strings +and +.Em must +be terminated by a +.Dv NULL +pointer. +The other functions take the environment for the new process image from the +external variable +.Va environ +in the current process. +.Pp +Some of these functions have special semantics. +.Pp +The functions +.Fn execlp , +.Fn execvp , +and +.Fn execvP +will duplicate the actions of the shell in searching for an executable file +if the specified file name does not contain a slash +.Dq Li / +character. +For +.Fn execlp +and +.Fn execvp , +search path is the path specified in the environment by +.Dq Ev PATH +variable. +If this variable is not specified, +the default path is set according to the +.Dv _PATH_DEFPATH +definition in +.In paths.h , +which is set to +.Dq Ev /usr/bin:/bin . +For +.Fn execvP , +the search path is specified as an argument to the function. +In addition, certain errors are treated specially. +.Pp +If an error is ambiguous (for simplicity, we shall consider all +errors except +.Er ENOEXEC +as being ambiguous here, although only the critical error +.Er EACCES +is really ambiguous), +then these functions will act as if they stat the file to determine +whether the file exists and has suitable execute permissions. +If it does, they will return immediately with the global variable +.Va errno +restored to the value set by +.Fn execve . +Otherwise, the search will be continued. +If the search completes without performing a successful +.Fn execve +or terminating due to an error, +these functions will return with the global variable +.Va errno +set to +.Er EACCES +or +.Er ENOENT +according to whether at least one file with suitable execute permissions +was found. +.Pp +If the header of a file is not recognized (the attempted +.Fn execve +returned +.Er ENOEXEC ) , +these functions will execute the shell with the path of +the file as its first argument. +(If this attempt fails, no further searching is done.) +.Pp +The function +.Fn exect +executes a file with the program tracing facilities enabled (see +.Xr ptrace 2 ) . +.Sh RETURN VALUES +If any of the +.Fn exec +functions returns, an error will have occurred. +The return value is \-1, and the global variable +.Va errno +will be set to indicate the error. +.Sh FILES +.Bl -tag -width /bin/sh -compact +.It Pa /bin/sh +The shell. +.El +.Sh COMPATIBILITY +Historically, the default path for the +.Fn execlp +and +.Fn execvp +functions was +.Dq Pa :/bin:/usr/bin . +This was changed to place the current directory last to enhance system +security. +.Pp +The behavior of +.Fn execlp +and +.Fn execvp +when errors occur while attempting to execute the file is not quite historic +practice, and has not traditionally been documented and is not specified +by the +.Tn POSIX +standard. +.Pp +Traditionally, the functions +.Fn execlp +and +.Fn execvp +ignored all errors except for the ones described above and +.Er ETXTBSY , +upon which they retried after sleeping for several seconds, and +.Er ENOMEM +and +.Er E2BIG , +upon which they returned. +They now return for +.Er ETXTBSY , +and determine existence and executability more carefully. +In particular, +.Er EACCES +for inaccessible directories in the path prefix is no longer +confused with +.Er EACCES +for files with unsuitable execute permissions. +In +.Bx 4.4 , +they returned upon all errors except +.Er EACCES , +.Er ENOENT , +.Er ENOEXEC +and +.Er ETXTBSY . +This was inferior to the traditional error handling, +since it breaks the ignoring of errors for path prefixes +and only improves the handling of the unusual ambiguous error +.Er EFAULT +and the unusual error +.Er EIO . +The behaviour was changed to match the behaviour of +.Xr sh 1 . +.Sh ERRORS +The +.Fn execl , +.Fn execle , +.Fn execlp , +.Fn execvp +and +.Fn execvP +functions +may fail and set +.Va errno +for any of the errors specified for the library functions +.Xr execve 2 +and +.Xr malloc 3 . +.Pp +The +.Fn exect +and +.Fn execv +functions +may fail and set +.Va errno +for any of the errors specified for the library function +.Xr execve 2 . +.Sh SEE ALSO +.Xr sh 1 , +.Xr execve 2 , +.Xr fork 2 , +.Xr ktrace 2 , +.Xr ptrace 2 , +.Xr environ 7 +.Sh STANDARDS +The +.Fn execl , +.Fn execv , +.Fn execle , +.Fn execlp +and +.Fn execvp +functions +conform to +.St -p1003.1-88 . +The +.Fn execvP +function first appeared in +.Fx 5.2 . |