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Annotation of coherent/d/bin/env.c, revision 1.1

1.1     ! root        1: static char _version[]="env version 1.0";
        !             2: /*
        !             3:  * env - execute a command in an environment
        !             4:  *
        !             5:  * usage: env [-] [VARIABLE=value ...] [command args]
        !             6:  *
        !             7:  * Executes "command" with "args", modifying the existing environment
        !             8:  * by doing the requested assignments.  The "-" option means that the
        !             9:  * environment should be _replaced_ with the list assignements, otherwise
        !            10:  * the assignments are added to the environment.
        !            11:  * If "command" is ommitted, the resulting environment is printed.
        !            12:  */
        !            13: 
        !            14: #include <stdio.h>
        !            15: #include <string.h>
        !            16: #include <errno.h>
        !            17: 
        !            18: #define BIG_NUMBER 2048
        !            19: #define TRUE (1==1)
        !            20: #define FALSE (1==0)
        !            21: #define VAR_SEPERATOR '='      /* Seperates an environment variable
        !            22:                                   from its value.  */
        !            23: 
        !            24: void parse_args();
        !            25: int arglen();
        !            26: char **argcpy();
        !            27: char **envncat();
        !            28: int is_assignment();
        !            29: 
        !            30: /* Flags that tell us about our arguments */
        !            31: int replace_env = FALSE;
        !            32: int have_command = FALSE;
        !            33: 
        !            34: int assignment_count;  /* Number of assignments to add to environment.  */
        !            35: char *first_assignment_argument = NULL;
        !            36: 
        !            37: int i; /* Generic index, used repeatedly */
        !            38: 
        !            39: char **new_argv;       /* Build new command line here.  */
        !            40: char **new_envp;       /* Build the new environment here.  */
        !            41: 
        !            42: 
        !            43: void
        !            44: main(argc, argv, envp)
        !            45:        int argc;
        !            46:        char *argv[];
        !            47:        char *envp[];
        !            48: {
        !            49: /* Parse arguments.  */
        !            50:        parse_args(argc, argv);
        !            51: 
        !            52: /* Build the new environment.  */
        !            53: 
        !            54:        if (! replace_env) {
        !            55:                /* Make enough space for the disjoint union of the two sets of
        !            56:                 * environment assignments.  This is a guarenteed upper bound.
        !            57:                 */
        !            58:                new_envp = (char **) malloc( sizeof(char *)
        !            59:                                             * (arglen(envp)
        !            60:                                                + assignment_count + 1)
        !            61:                                           );
        !            62:                argcpy(new_envp, envp);
        !            63:        } else {
        !            64:                /* Otherwise, we only need enough space for the new
        !            65:                 * environment.
        !            66:                 */
        !            67:                new_envp = (char **) malloc( sizeof(char *)
        !            68:                                             * (assignment_count + 1)
        !            69:                                           );
        !            70:        } /* if (! replace_env) */
        !            71: 
        !            72: 
        !            73:        envncat(new_envp, first_assignment_argument, assignment_count);
        !            74: 
        !            75: 
        !            76: /* Do something--either a command or print the environment.  */
        !            77:        if (have_command) {
        !            78:                execvep(new_argv[0], new_argv, new_envp);
        !            79:                perror(new_argv[0]);
        !            80:                exit(1);
        !            81:        } else {
        !            82:                char **pntr;
        !            83: 
        !            84:                for (pntr = new_envp; *pntr != NULL; ++pntr){
        !            85:                        printf("%s\n", *pntr);
        !            86:                } /* for pntr in new_envp */
        !            87: 
        !            88:        } /* if have_command */
        !            89: 
        !            90:        exit(0);
        !            91: }
        !            92: 
        !            93: 
        !            94: void
        !            95: parse_args(argc, argv)
        !            96:        int argc;
        !            97:        char *argv[];
        !            98: {
        !            99:        int current_arg;
        !           100: 
        !           101:        if (argc > 1) {
        !           102:                current_arg = 1; /* Start looking at the first argument.  */
        !           103: 
        !           104:                /* - option -- Replace the existing environment.  */
        !           105:                if (strcmp(argv[current_arg], "-") == 0) {
        !           106:                        replace_env = TRUE;
        !           107:                        ++current_arg;
        !           108:                } /* if first argument is "-" */
        !           109: 
        !           110:                /* Count the number of arguments which are assignments.  */
        !           111:                for (assignment_count = 0;
        !           112:                     current_arg < argc;
        !           113:                     current_arg++, assignment_count++) {
        !           114: 
        !           115:                        if (! is_assignment(argv[current_arg])) {
        !           116:                                break;
        !           117:                        }
        !           118: 
        !           119:                        if (first_assignment_argument == NULL) {
        !           120:                                first_assignment_argument = &argv[current_arg];
        !           121:                        }
        !           122: 
        !           123:                } /* for (Count the assignments on the command line.  ) */
        !           124: 
        !           125: 
        !           126:                if ( current_arg < argc ) {
        !           127:                        /* We broke out of the assignment couting loop
        !           128:                         * early--this must be a command.
        !           129:                         */
        !           130:                        new_argv = &argv[current_arg];
        !           131:                        have_command = TRUE;
        !           132:                } /* if ( current_arg <= argc ) */
        !           133: 
        !           134:        } /* if there are any args */
        !           135: 
        !           136: } /* void parse_args() */
        !           137: 
        !           138: 
        !           139: 
        !           140: /* Count the number of arguments in an argument vector.
        !           141:  * arg_vector MUST be NULL terminated!
        !           142:  */
        !           143: int
        !           144: arglen(arg_vector)
        !           145:        char **arg_vector;
        !           146: {
        !           147:        int count;
        !           148:        
        !           149:        for (count = 0; arg_vector[count] != NULL; ++count) {
        !           150:        }
        !           151: 
        !           152:        return(count);
        !           153: } /* arglen() */
        !           154: 
        !           155: 
        !           156: /* Copy src argument vector to dest argument vector (pointer copy only).
        !           157:  */
        !           158: char **
        !           159: argcpy(dest, src)
        !           160:        char **dest, **src;
        !           161: {
        !           162:        while (*src != NULL) {
        !           163:                *dest++ = *src++;
        !           164:        } /* while (walk two pointers down envp and new_envp) */
        !           165:        *dest = NULL;
        !           166:        return (dest);
        !           167: } /* char **argcpy() */
        !           168: 
        !           169: 
        !           170: 
        !           171: 
        !           172: /* Merge one environment onto another, overwriting duplicate
        !           173:  * variable names.  Compare at most n patterns.
        !           174:  */
        !           175: char **
        !           176: envncat(dest, src, n)
        !           177:        char **dest, **src;
        !           178:        int n;
        !           179: {
        !           180:        char **dest_walker;
        !           181:        char *sep_loc;  /* Seperator ("=") location in assignment */
        !           182:        int i;
        !           183:        int name_size;  /* Number of characters in a given variable name */
        !           184: 
        !           185:        for (i=0; *src != NULL && i < n; ++i, ++src) {
        !           186: 
        !           187:                /* Extract the variable name from the assignment *src.  */
        !           188:                if ((sep_loc = strchr(*src, VAR_SEPERATOR)) == NULL) {
        !           189:                        fprintf(stderr,
        !           190:                                "Programming error:  %s is not an assignment\n",
        !           191:                                *src);
        !           192:                        exit(1);
        !           193:                }
        !           194:                name_size = sep_loc - *src;
        !           195:                
        !           196:                /* Look for variable part of *src in dest.
        !           197:                 * Point at end if not found.
        !           198:                 */
        !           199:                for(dest_walker = dest; *dest_walker != NULL; ++dest_walker) {
        !           200: 
        !           201:                        /* NB: the + 1 is so the "=" is compared too.  */
        !           202:                        if(strncmp(*dest_walker, *src, name_size + 1) == 0) {
        !           203:                                /* We have found an exact match.  */
        !           204:                                break;
        !           205:                        } /* if *dest_walker and *src are same variable */
        !           206: 
        !           207:                } /* for Walk down dest environment */
        !           208: 
        !           209:                /* Checkpoint - *dest_walker either matches *src or is NULL.  */
        !           210: 
        !           211:                /* WARNING: possible memory leak--
        !           212:                 *          *dest_walker is always clobbered.
        !           213:                 *           Usually *dest_walker was copied from global
        !           214:                 *           envp, so it isn't really lost memory.
        !           215:                 */
        !           216:                *dest_walker = *src;
        !           217: 
        !           218:        } /* for (i=0; *src != NULL && i < n; ++i, ++src) */
        !           219: 
        !           220:        return(dest);
        !           221: } /* char ** envncat() */
        !           222: 
        !           223: int
        !           224: is_assignment(s)
        !           225:        char *s;
        !           226: {
        !           227:        if ( strchr(s, VAR_SEPERATOR) != NULL ) {
        !           228:                return(TRUE);
        !           229:        } else {
        !           230:                return(FALSE);
        !           231:        }
        !           232: 
        !           233: } /* int is_assignment() */

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