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EXEC(3)                     BSD Programmer's Manual                    EXEC(3)

N\bNA\bAM\bME\bE
     e\bex\bxe\bec\bcl\bl, e\bex\bxe\bec\bcl\blp\bp, e\bex\bxe\bec\bcl\ble\be, e\bex\bxe\bec\bct\bt, e\bex\bxe\bec\bcv\bv, e\bex\bxe\bec\bcv\bvp\bp - execute a file

S\bSY\bYN\bNO\bOP\bPS\bSI\bIS\bS
     #\b#i\bin\bnc\bcl\blu\bud\bde\be <\b<u\bun\bni\bis\bst\btd\bd.\b.h\bh>\b>

     _\be_\bx_\bt_\be_\br_\bn _\bc_\bh_\ba_\br _\b*_\b*_\be_\bn_\bv_\bi_\br_\bo_\bn_\b;

     _\bi_\bn_\bt
     e\bex\bxe\bec\bcl\bl(_\bc_\bo_\bn_\bs_\bt _\bc_\bh_\ba_\br _\b*_\bp_\ba_\bt_\bh, _\bc_\bo_\bn_\bs_\bt _\bc_\bh_\ba_\br _\b*_\ba_\br_\bg, _\b._\b._\b.);

     _\bi_\bn_\bt
     e\bex\bxe\bec\bcl\blp\bp(_\bc_\bo_\bn_\bs_\bt _\bc_\bh_\ba_\br _\b*_\bf_\bi_\bl_\be, _\bc_\bo_\bn_\bs_\bt _\bc_\bh_\ba_\br _\b*_\ba_\br_\bg, _\b._\b._\b.);

     _\bi_\bn_\bt
     e\bex\bxe\bec\bcl\ble\be(_\bc_\bo_\bn_\bs_\bt _\bc_\bh_\ba_\br _\b*_\bp_\ba_\bt_\bh, _\bc_\bo_\bn_\bs_\bt _\bc_\bh_\ba_\br _\b*_\ba_\br_\bg, _\b._\b._\b., _\bc_\bh_\ba_\br _\b*_\bc_\bo_\bn_\bs_\bt _\be_\bn_\bv_\bp_\b[_\b]);

     _\bi_\bn_\bt
     e\bex\bxe\bec\bct\bt(_\bc_\bo_\bn_\bs_\bt _\bc_\bh_\ba_\br _\b*_\bp_\ba_\bt_\bh, _\bc_\bh_\ba_\br _\b*_\bc_\bo_\bn_\bs_\bt _\ba_\br_\bg_\bv_\b[_\b]);

     _\bi_\bn_\bt
     e\bex\bxe\bec\bcv\bv(_\bc_\bo_\bn_\bs_\bt _\bc_\bh_\ba_\br _\b*_\bp_\ba_\bt_\bh, _\bc_\bh_\ba_\br _\b*_\bc_\bo_\bn_\bs_\bt _\ba_\br_\bg_\bv_\b[_\b]);

     _\bi_\bn_\bt
     e\bex\bxe\bec\bcv\bvp\bp(_\bc_\bo_\bn_\bs_\bt _\bc_\bh_\ba_\br _\b*_\bf_\bi_\bl_\be, _\bc_\bh_\ba_\br _\b*_\bc_\bo_\bn_\bs_\bt _\ba_\br_\bg_\bv_\b[_\b]);

D\bDE\bES\bSC\bCR\bRI\bIP\bPT\bTI\bIO\bON\bN
     The e\bex\bxe\bec\bc 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 execve(2).  (See the manual page for execve
     for detailed information about the replacement of the current process.)

     The initial argument for these functions is the pathname of a file which
     is to be executed.

     The _\bc_\bo_\bn_\bs_\bt _\bc_\bh_\ba_\br _\b*_\ba_\br_\bg and subsequent ellipses in the e\bex\bxe\bec\bcl\bl(), e\bex\bxe\bec\bcl\blp\bp(), and
     e\bex\bxe\bec\bcl\ble\be() functions can be thought of as _\ba_\br_\bg_\b0, _\ba_\br_\bg_\b1, ..., _\ba_\br_\bg_\bn. 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 _\bm_\bu_\bs_\bt be terminated
     by a NULL pointer.

     The e\bex\bxe\bec\bct\bt(), e\bex\bxe\bec\bcv\bv(), and e\bex\bxe\bec\bcv\bvp\bp() 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 begin executed.  The array of pointers
     m\bmu\bus\bst\bt be terminated by a NULL pointer.

     The e\bex\bxe\bec\bcl\ble\be() and e\bex\bxe\bec\bct\bt() functions also specify the environment of the
     executed process by following the NULL pointer that terminates the list
     of arguments in the parameter list or the pointer to the argv array with
     an additional parameter.  This additional parameter is an array of point-
     ers to null-terminated strings and _\bm_\bu_\bs_\bt be terminated by a NULL pointer.
     The other functions take the environment for the new process image from
     the external variable _\be_\bn_\bv_\bi_\br_\bo_\bn in the current process.

     Some of these functions have special semantics.

     The functions e\bex\bxe\bec\bcl\blp\bp() and e\bex\bxe\bec\bcv\bvp\bp() will duplicate the actions of the
     shell in searching for an executable file if the specified file name does
     not contain a slash ``/'' character.  The search path is the path speci-
     fied in the environment by ``PATH'' variable.  If this variable isn't
     specified, the default path ``/bin:/usr/bin:'' is used.  In addtion, cer-
     tain errors are treated specially.

     If permission is denied for a file (the attempted execve returned
     EACCES), these functions will continue searching the rest of the search
     path.  If no other file is found, however, they will return with the
     global variable _\be_\br_\br_\bn_\bo set to EACCES.

     If the header of a file isn't recognized (the attempted execve returned
     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.)

     If the file is currently busy (the attempted execve returned ETXTBUSY),
     these functions will sleep for several seconds, periodically re-
     attempting to execute the file.

     The function e\bex\bxe\bec\bct\bt() executes a file with the program tracing facilities
     enabled (see ptrace(2)).

R\bRE\bET\bTU\bUR\bRN\bN V\bVA\bAL\bLU\bUE\bES\bS
     If any of the exec functions returns, an error will have occurred.  The
     return value is -1, and the global variable _\be_\br_\br_\bn_\bo will be set to indicate
     the error.

F\bFI\bIL\bLE\bES\bS
     /bin/sh  The shell.

E\bER\bRR\bRO\bOR\bRS\bS
     E\bEx\bxe\bec\bcl\bl(), e\bex\bxe\bec\bcl\ble\be(), e\bex\bxe\bec\bcl\blp\bp() and e\bex\bxe\bec\bcv\bvp\bp() may fail and set _\be_\br_\br_\bn_\bo for any
     of the errors specified for the library functions execve(2) and
     malloc(3).

     E\bEx\bxe\bec\bct\bt() and e\bex\bxe\bec\bcv\bv() may fail and set _\be_\br_\br_\bn_\bo for any of the errors speci-
     fied for the library function execve(2).

S\bSE\bEE\bE A\bAL\bLS\bSO\bO
     sh(1),  execve(2),  fork(2),  trace(2),  environ(7),  ptrace(2),
     environ(7),

C\bCO\bOM\bMP\bPA\bAT\bTI\bIB\bBI\bIL\bLI\bIT\bTY\bY
     Historically, the default path for the e\bex\bxe\bec\bcl\blp\bp() and e\bex\bxe\bec\bcv\bvp\bp() functions
     was ``_\b:_\b/_\bb_\bi_\bn_\b:_\b/_\bu_\bs_\br_\b/_\bb_\bi_\bn''. This was changed to place the current directory
     last to enhance system security.

     The behavior of e\bex\bxe\bec\bcl\blp\bp() and e\bex\bxe\bec\bcv\bvp\bp() when errors occur while attempting
     to execute the file is historic practice, but has not traditionally been
     documented and is not specified by the POSIX standard.

     Traditionally, the functions e\bex\bxe\bec\bcl\blp\bp() and e\bex\bxe\bec\bcv\bvp\bp() ignored all errors ex-
     cept for the ones described above and ENOMEM and E2BIG, upon which they
     returned.  They now return if any error other than the ones described
     above occurs.

S\bST\bTA\bAN\bND\bDA\bAR\bRD\bDS\bS
     E\bEx\bxe\bec\bcl\bl(), e\bex\bxe\bec\bcv\bv(), e\bex\bxe\bec\bcl\ble\be(), e\bex\bxe\bec\bcl\blp\bp() and e\bex\bxe\bec\bcv\bvp\bp() conform to IEEE
     Std1003.1-1988 (``POSIX'').

4.4BSD                           June 4, 1993                                2