1EXEC(3) 386BSD Programmer's Manual EXEC(3) 2 3NNAAMMEE 4 eexxeeccll, eexxeeccllpp, eexxeeccllee, eexxeecctt, eexxeeccvv, eexxeeccvvpp - execute a file 5 6SSYYNNOOPPSSIISS 7 ##iinncclluuddee <<uunniissttdd..hh>> 8 9 _e_x_t_e_r_n _c_h_a_r **_e_n_v_i_r_o_n; 10 11 _i_n_t 12 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, ...) 13 14 _i_n_t 15 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, ...) 16 17 _i_n_t 18 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[]) 19 20 _i_n_t 21 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[]) 22 23 _i_n_t 24 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[]) 25 26 _i_n_t 27 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[]) 28 29DDEESSCCRRIIPPTTIIOONN 30 The eexxeecc family of functions replaces the current process image with a 31 new process image. The functions described in this manual page are 32 front-ends for the function execve(2). (See the manual page for execve 33 for detailed information about the replacement of the current process.) 34 35 The initial argument for these functions is the pathname of a file which 36 is to be executed. 37 38 The _c_o_n_s_t _c_h_a_r *_a_r_g and subsequent ellipses in the eexxeeccll(), eexxeeccllpp(), and 39 eexxeeccllee() functions can be thought of as _a_r_g_0, _a_r_g_1, ..., _a_r_g_n. Together 40 they describe a list of one or more pointers to null-terminated strings 41 that represent the argument list available to the executed program. The 42 first argument, by convention, should point to the file name associated 43 with the file being executed. The list of arguments _m_u_s_t be terminated 44 by a NULL pointer. 45 46 The eexxeecctt(), eexxeeccvv(), and eexxeeccvvpp() functions provide an array of pointers 47 to null-terminated strings that represent the argument list available to 48 the new program. The first argument, by convention, should point to the 49 file name associated with the file begin executed. The array of pointers 50 mmuusstt be terminated by a NULL pointer. 51 52 The eexxeeccllee() and eexxeecctt() functions also specify the environment of the 53 executed process by following the NULL pointer that terminates the list 54 of arguments in the parameter list or the pointer to the argv array with 55 an additional parameter. This additional parameter is an array of 56 pointers to null-terminated strings and _m_u_s_t be terminated by a NULL 57 pointer. The other functions take the environment for the new process 58 image from the external variable _e_n_v_i_r_o_n in the current process. 59 60 Some of these functions have special semantics. 61 62 The functions eexxeeccllpp() and eexxeeccvvpp() will duplicate the actions of the 63 shell in searching for an executable file if the specified file name does 64 not contain a slash ``/'' character. The search path is the path 65 specified in the environment by ``PATH'' variable. If this variable 66 isn't specified, the default path ``/bin:/usr/bin:'' is used. In 67 addtion, certain errors are treated specially. 68 69 If permission is denied for a file (the attempted execve returned 70 EACCES), these functions will continue searching the rest of the search 71 path. If no other file is found, however, they will return with the 72 global variable _e_r_r_n_o set to EACCES. 73 74 If the header of a file isn't recognized (the attempted execve returned 75 ENOEXEC), these functions will execute the shell with the path of the 76 file as its first argument. (If this attempt fails, no further searching 77 is done.) 78 79 If the file is currently busy (the attempted execve returned ETXTBUSY), 80 these functions will sleep for several seconds, periodically re- 81 attempting to execute the file. 82 83 The function eexxeecctt() executes a file with the program tracing facilities 84 enabled (see ptrace(2)). 85 86RREETTUURRNN VVAALLUUEESS 87 If any of the exec functions returns, an error will have occurred. The 88 return value is -1, and the global variable _e_r_r_n_o will be set to indicate 89 the error. 90 91FFIILLEESS 92 /bin/sh The shell. 93 94EERRRROORRSS 95 EExxeeccll(), eexxeeccllee(), eexxeeccllpp() and eexxeeccvvpp() may fail and set _e_r_r_n_o for any 96 of the errors specified for the library functions execve(2) and 97 malloc(3). 98 99 EExxeecctt() and eexxeeccvv() may fail and set _e_r_r_n_o for any of the errors 100 specified for the library function execve(2). 101 102SSEEEE AALLSSOO 103 sh(1), execve(2), fork(2), trace(2), environ(7), ptrace(2), 104 environ(7), 105 106CCOOMMPPAATTIIBBIILLIITTYY 107 Historically, the default path for the eexxeeccllpp() and eexxeeccvvpp() functions 108 was ``:/_b_i_n:/_u_s_r/_b_i_n''. This was changed to place the current directory 109 last to enhance system security. 110 111 The behavior of eexxeeccllpp() and eexxeeccvvpp() when errors occur while attempting 112 to execute the file is historic practice, but has not traditionally been 113 documented and is not specified by the POSIX standard. 114 115 Traditionally, the functions eexxeeccllpp() and eexxeeccvvpp() ignored all errors 116 except for the ones described above and ENOMEM and E2BIG, upon which they 117 returned. They now return if any error other than the ones described 118 above occurs. 119 120SSTTAANNDDAARRDDSS 121 EExxeeccll(), eexxeeccvv(), eexxeeccllee(), eexxeeccllpp() and eexxeeccvvpp() conform to IEEE 122 Std1003.1-1988 (``POSIX''). 123 124BSD Experimental April 19, 1991 2 125 126 127 128 129 130 131 132 133