crontab.c

这是一个我自己仿照linux下cron程序写的精简版的cron

#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <sys/file.h>
#include <sys/stat.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <unistd.h>
#include <time.h>
#include <utime.h>
#include <stdio.h>
#include <pwd.h>
#include <unistd.h>
#include <string.h>
#include <dirent.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/wait.h>
#include "crontab.h"


static struct passwd *pw;
static char  *User;
static char  *RealUser;
static  char   ProgramName[] = "my_crontab";
static enum opt_t Option;
static char  Filename[MAX_FNAME];
static char  Directory[MAX_FNAME];
static FILE  *NewCrontab = NULL;
static  pid_t  Pid;
static  char *getoptarg = "u:ler";
static  char tn[MAX_FNAME];


static void usage(char *msg)
{
        fprintf(stderr, "%s: usage error: %s\n", ProgramName, msg);
        fprintf(stderr, "usage:\t%s [-u user] file\n", ProgramName);
        fprintf(stderr, "\t%s [-u user] { -e | -l | -r }\n", ProgramName);
        fprintf(stderr, "\t\t(default operation is replace, per 1003.2)\n");
        fprintf(stderr, "\t-e\t(edit user's crontab)\n");
        fprintf(stderr, "\t-l\t(list user's crontab)\n");
        fprintf(stderr, "\t-r\t(delete user's crontab)\n");
        exit(0);
}


static void parse_args(int argc,char **argv)
{
        int  argch;
        struct stat statbuf;

        /* get the user id */
        if (!(pw = getpwuid(getuid()))) {
                fprintf(stderr, "%s: your UID isn't in the passwd file.\n",
                        ProgramName);
                fprintf(stderr, "bailing out.\n");
                exit(1);
        }
        /* dup the user id*/
        if (((User=strdup(pw->pw_name)) == NULL)) {
                fprintf(stderr, "Memory allocation error\n");
                exit(1);
        }
        Filename[0] = '\0';
        Option = opt_unknown;

        while ((argch = getopt(argc, argv, getoptarg)) != EOF) {
                switch (argch) {
                        case 'u':
                                /*return a pointer to a structure containing the broken field of a line from
                                 etc/passwd for the entry that match the user name*/
                                if (!(pw = getpwnam(optarg)))/*check if the user is efficiency*/
                                {
                                        fprintf(stderr, "%s:  user `%s' unknown\n",
                                                ProgramName, optarg);
                                        exit(1);
                                }
                                /*if the user is root and the user is not the name after -u*/
                                if ((getuid() != ROOT_UID) &&
                                                (getuid() != pw->pw_uid)) {
                                        fprintf(stderr,
                                                "Your are not root or the user that own this crontab\n");
                                        exit(1);
                                }
                                free(User);

                                if ((User=strdup(pw->pw_name)) == NULL) {
                                        fprintf(stderr, "Memory allocation error\n");
                                        exit(1);
                                }
                                break;
                        case 'l':
                                if (Option != opt_unknown)
                                        usage("only one operation permitted");
                                Option = opt_list;
                                break;
                        case 'r':
                                if (Option != opt_unknown)
                                        usage("only one operation permitted");
                                Option = opt_delete;
                                break;
                        case 'e':
                                if (Option != opt_unknown)
                                        usage("only one operation permitted");
                                Option = opt_edit;
                                break;
                        default:
                                usage("unrecognized option");
                }
        }

        endpwent();

        if (Option != opt_unknown) {
                if (argv[optind] != NULL) {
                        usage("no arguments permitted after this option");
                }
        } else {
                if (argv[optind] != NULL) {
                        Option = opt_replace;
                        (void) strncpy (Filename, argv[optind], (sizeof Filename)-1);
                        Filename[(sizeof Filename)-1] = '\0';
                } else {
                        usage("file name must be specified for replace");
                }
        }

        if (Option == opt_replace) {
                if (!(NewCrontab = fopen(Filename, "r"))) {
                        perror(Filename);
                        exit(1);
                }
                /* Make sure we opened a normal file. */
                if (fstat(fileno(NewCrontab), &statbuf) < 0) {
                        perror("fstat");
                        exit(1);
                }
                if (!S_ISREG(statbuf.st_mode)) {
                        fprintf(stderr, "%s: Not a regular file.\n", Filename);
                        exit(1);
                }
        }

}



/******************************* cmd here *******************************/

static void list_cmd()
{
        FILE *f;
        int ch;
        char n[MAX_FNAME];

        (void) snprintf(n, MAX_FNAME, CRON_TAB(User));
        if (!(f = fopen(n, "r"))) {
                /*no such file or dir*/
                if (errno == ENOENT)
                        fprintf(stderr, "no crontab for %s\n", User);
                else
                        perror(n);
                exit(1);
        }

        while (EOF != (ch = getc(f)))
                putchar(ch);
        fclose(f);
}



static void delete_cmd()
{
        char n[MAX_FNAME];

        (void) snprintf(n, MAX_FNAME, CRON_TAB(User));
        if (unlink(n)) {
                if (errno == ENOENT)
                        fprintf(stderr, "no crontab for %s\n", User);
                else
                        perror(n);
                exit(1);
        }
        //poke_daemon();
}



static int get_next_token(char *buffer,char *line,int *pt)
{
        int i = 0;
        while (line[*pt] == ' ' || line[*pt] == '\t') {
                (*pt)++;
        }

        if (line[*pt] == ',') {
                (*pt)++;
                return 4;
        } else if (isdigit(line[*pt])) {
                buffer[i++] = line[*pt];
                (*pt)++;
                while (isdigit(line[*pt])) {
                        buffer[i++] = line[*pt];
                        (*pt)++;
                }
                if (line[*pt] == ',') {
                        buffer[i] = '\0';
                        (*pt)++;
                        return 3;
                } else if (line[*pt] == ' ' || line[*pt] == '\t') {
                        buffer[i] = '\0';
                        while(line[*pt] == ' ' || line[*pt] == '\t')
                                (*pt)++;
                        if(line[*pt] == ',') {
                                (*pt)++;
                                return 3;
                        } else
                                return 1;
                } else {
                        return 5;
                }
        } else if (line[*pt] == '*') {
                (*pt)++;
                return 2;
        } else {
                return 5;
        }
}


static int check_number(char *buffer,int i)
{
        int num;
        int value[5][2] = {{0,59},{0,23},{1,31},{1,12},{0,6}};

        num = atoi(buffer);
        if(num >= value[i][0] && num <= value[i][1])
                return 1;
        else
                return 0;
}



static int check_error()
{
        char line[MAX_LINE];
        char buffer[MAX_FNAME];
        char * f;
        int pt = 0;
        int i = 0;
        int flag = 0;
        int can_gets = 0;
        int finish = 0;

        while((f = fgets(line,MAX_LINE,NewCrontab)) != NULL) {
                can_gets = 1;
                pt = 0;
                /****** to see if the line is an empty line or a comment line **/
                while(line[pt] == ' ' || line[pt] == '\t')
                        pt++;
                if(line[pt] == '#' || line[pt] == '\n')
                        continue;
                /*************** divide the date in to five part *****************/
                for(; i < 5; i++) {
                        finish = 0;
                        while(1) {
                                flag = get_next_token(buffer,line,&pt);
                                switch(flag) {
                                        case 1:
                                                if(!check_number(buffer,i)) {
                                                        fprintf(stderr,"%s\n",line);
                                                        fprintf(stderr,"Some of the number of your crontab is excess the legal range.\n");
                                                        fprintf(stderr,"1) Minute: 0 ~ 59.\n");
                                                        fprintf(stderr,"2) Hour: 0 ~ 23.\n");
                                                        fprintf(stderr,"3) Day of month: 1 ~ 31.\n");
                                                        fprintf(stderr,"4) Month of year: 1 ~ 12.\n");
                                                        fprintf(stderr,"5) Day of week: 0 ~ 6.\n");
                                                        return 0;
                                                }
                                                finish = 1;
                                                break;
                                        case 2:
                                                finish = 1;
                                                break;
                                        case 3:
                                                finish = 0;
                                                if(!check_number(buffer,i)) {
                                                        fprintf(stderr,"%s\n",line);
                                                        fprintf(stderr,"Some of the number of your crontab is excess the legal range!\n");
                                                        return 0;
                                                }
                                                break;
                                        case 4:
                                                fprintf(stderr,"%s\n",line);
                                                fprintf(stderr,"Empty term is not allow!\n");
                                                return 0;
                                                break;
                                        case 5:
                                                fprintf(stderr,"%s\n",line);
                                                fprintf(stderr,"Unexpected word here!\n");
                                                return 0;
                                                break;
                                        default:
                                                return 0;
                                                break;
                                }
                                if(finish)
                                        break;
                        }
                }
                i = 0;
        }
        return 1;
}










static int replace_cmd()
{
        char n[MAX_FNAME], envstr[MAX_ENVSTR];
        FILE *tmp;
        int ch, eof, fd;
        int markfd;