Fresh Fish 4/FreshFish_May-June1994.bin/bbs/gnu/ixemul-39.47-env-bin.lha/man/cat3/exec.0

Text File | 1993-12-07 | 6.3 KB | 133 lines

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

NNAAMMEE
     eexxeeccll, eexxeeccllpp, eexxeeccllee, eexxeecctt, eexxeeccvv, eexxeeccvvpp - execute a file

SSYYNNOOPPSSIISS
     ##iinncclluuddee <<uunniissttdd..hh>>

     _e_x_t_e_r_n _c_h_a_r _*_*_e_n_v_i_r_o_n_;

     _i_n_t
     eexxeeccll(_c_o_n_s_t _c_h_a_r _*_p_a_t_h, _c_o_n_s_t _c_h_a_r _*_a_r_g, _._._.)

     _i_n_t
     eexxeeccllpp(_c_o_n_s_t _c_h_a_r _*_f_i_l_e, _c_o_n_s_t _c_h_a_r _*_a_r_g, _._._.)

     _i_n_t
     eexxeeccllee(_c_o_n_s_t _c_h_a_r _*_p_a_t_h, _c_o_n_s_t _c_h_a_r _*_a_r_g, _._._., _c_h_a_r _*_c_o_n_s_t _e_n_v_p_[_])

     _i_n_t
     eexxeecctt(_c_o_n_s_t _c_h_a_r _*_p_a_t_h, _c_h_a_r _*_c_o_n_s_t _a_r_g_v_[_])

     _i_n_t
     eexxeeccvv(_c_o_n_s_t _c_h_a_r _*_p_a_t_h, _c_h_a_r _*_c_o_n_s_t _a_r_g_v_[_])

     _i_n_t
     eexxeeccvvpp(_c_o_n_s_t _c_h_a_r _*_f_i_l_e, _c_h_a_r _*_c_o_n_s_t _a_r_g_v_[_])

DDEESSCCRRIIPPTTIIOONN
     The eexxeecc family of functions replaces the current process image with a
     new process image.  The functions described in this manual page are
     front­ends 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 _c_o_n_s_t _c_h_a_r _*_a_r_g and subsequent ellipses in the eexxeeccll(), eexxeeccllpp(), and
     eexxeeccllee() functions can be thought of as _a_r_g_0, _a_r_g_1, ..., _a_r_g_n. Together
     they describe a list of one or more pointers to null­terminated 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 _m_u_s_t be terminated
     by a NULL pointer.

     The eexxeecctt(), eexxeeccvv(), and eexxeeccvvpp() functions provide an array of pointers
     to null­terminated 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
     mmuusstt be terminated by a NULL pointer.

     The eexxeeccllee() and eexxeecctt() 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 null­terminated strings and _m_u_s_t be terminated by a NULL pointer.
     The other functions take the environment for the new process image from
     the external variable _e_n_v_i_r_o_n in the current process.

     Some of these functions have special semantics.

     The functions eexxeeccllpp() and eexxeeccvvpp() 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 _e_r_r_n_o 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 eexxeecctt() executes a file with the program tracing facilities
     enabled (see ptrace(2)).

RREETTUURRNN VVAALLUUEESS
     If any of the exec functions returns, an error will have occurred.  The
     return value is -1, and the global variable _e_r_r_n_o will be set to indicate
     the error.

FFIILLEESS
     /bin/sh  The shell.

EERRRROORRSS
     EExxeeccll(), eexxeeccllee(), eexxeeccllpp() and eexxeeccvvpp() may fail and set _e_r_r_n_o for any
     of the errors specified for the library functions execve(2) and
     malloc(3).

     EExxeecctt() and eexxeeccvv() may fail and set _e_r_r_n_o for any of the errors speci­
     fied for the library function execve(2).

SSEEEE AALLSSOO
     sh(1),  execve(2),  fork(2),  trace(2),  environ(7),  ptrace(2),
     environ(7),

CCOOMMPPAATTIIBBIILLIITTYY
     Historically, the default path for the eexxeeccllpp() and eexxeeccvvpp() functions
     was ``_:_/_b_i_n_:_/_u_s_r_/_b_i_n''. This was changed to place the current directory
     last to enhance system security.

     The behavior of eexxeeccllpp() and eexxeeccvvpp() 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 eexxeeccllpp() and eexxeeccvvpp() 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.

SSTTAANNDDAARRDDSS
     EExxeeccll(), eexxeeccvv(), eexxeeccllee(), eexxeeccllpp() and eexxeeccvvpp() conform to IEEE
     Std1003.1­1988 (``POSIX'').

BSD Experimental                April 19, 1991                               2