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Annotation of coherent/a/usr/man/COHERENT/execve, revision 1.1.1.1

1.1       root        1: 
                      2: 
                      3: execve()               COHERENT System Call              execve()
                      4: 
                      5: 
                      6: 
                      7: 
                      8: Execute a load module
                      9: 
                     10: eexxeeccvvee(_f_i_l_e, _a_r_g_v, _e_n_v)
                     11: cchhaarr *_f_i_l_e, *_a_r_g_v[], *_e_n_v[];
                     12: 
                     13: The COHERENT  system includes six functions  that allow a process
                     14: to execute another  executable file (or load module, as described
                     15: in the header  l.out.h).  execve specifies arguments as a single,
                     16: NULL-terminated array  of parameters, called  argv.  The argument
                     17: env is the address of an array of pointers to strings that define
                     18: file's environment.  This allows execve to pass a new environment
                     19: to the  program being executed.  For  more information on program
                     20: execution, see execl.
                     21: 
                     22: ***** Example *****
                     23: 
                     24: The  following example  demonstrates execve,  as well  as tmpnam,
                     25: getenv,  and  path.  It  finds  all lines  with  more than  LIMIT
                     26: characters and call MicroEMACS to edit them.
                     27: 
                     28: 
                     29: #include <stdio.h>
                     30: #include <path.h>
                     31: #include <sys/stat.h>
                     32: 
                     33: 
                     34: 
                     35: #define LIMIT 70
                     36: 
                     37: 
                     38: 
                     39: extern char *getenv(), **environ, *tempnam();
                     40: 
                     41: 
                     42: 
                     43: main(argc, argv)
                     44: char *argv[];
                     45: {
                     46:         /*                me     -e   tmp   file */
                     47:         char *cmda[5] = { NULL, "-e", NULL, NULL, NULL };
                     48:         FILE *ifp, *tmp;
                     49:         char line[256];
                     50:         int  ct, len;
                     51: 
                     52: 
                     53: 
                     54:         if ((NULL == (cmda[3] = argv[1])) ||
                     55:             (NULL == (ifp = fopen(argv[1], "r")))) {
                     56:                 fprintf(stderr, "Cannot open %s\n", argv[1]);
                     57:                 exit(1);
                     58:         }
                     59: 
                     60: 
                     61: 
                     62: 
                     63: 
                     64: COHERENT Lexicon                                           Page 1
                     65: 
                     66: 
                     67: 
                     68: 
                     69: execve()               COHERENT System Call              execve()
                     70: 
                     71: 
                     72: 
                     73: 
                     74:         if (cmda[0] = path(getenv("PATH"), "me", AEXEC) == NULL) {
                     75:                 fprintf(stderr, "Cannot locate me\n");
                     76:                 exit(1);
                     77:         }
                     78: 
                     79: 
                     80: 
                     81:         if (NULL == (tmp = fopen((cmda[2] = tempnam(NULL, "lng")), "w"))) {
                     82:                 fprintf(stderr, "Cannot open tmpfile\n");
                     83:                 exit(1);
                     84:         }
                     85: 
                     86: 
                     87: 
                     88:         for (ct = 1; NULL != fgets(line, sizeof(line), ifp); ct++)
                     89:                 if (((len = strlen(line)) > LIMIT) ||
                     90:                     ('\n' != line[len -1]))
                     91:                         fprintf(tmp, "%d: %d characters long\n", ct, len);
                     92: 
                     93: 
                     94: 
                     95:         fclose(tmp);
                     96:         fclose(ifp);
                     97: 
                     98: 
                     99: 
                    100:         if (execve(cmda[0], cmda, environ) < 0) {
                    101:                 fprintf(stderr, "cannot execute me\n");
                    102:                 exit(1);
                    103:         }
                    104:         /* We never reach here ! */
                    105: }
                    106: 
                    107: 
                    108: ***** See Also *****
                    109: 
                    110: COHERENT system calls, environ, execution
                    111: 
                    112: ***** Diagnostics *****
                    113: 
                    114: execve does not return  if successful.  It returns -1 for errors,
                    115: such as file  being nonexistent, not accessible with execute per-
                    116: mission, having a bad format, or too large to fit in memory.
                    117: 
                    118: 
                    119: 
                    120: 
                    121: 
                    122: 
                    123: 
                    124: 
                    125: 
                    126: 
                    127: 
                    128: 
                    129: 
                    130: COHERENT Lexicon                                           Page 2
                    131: 
                    132: 

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