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Annotation of researchv9/cmd/emacs/findtty.c, revision 1.1.1.1

1.1       root        1: #include <stdio.h>
                      2: #include "stddefs.h"
                      3: #include <sys/types.h>
                      4: #include <sys/stat.h>
                      5: #include <utmp.h>
                      6: 
                      7: /* Returns a pointer to a character string containing the tty name of a
                      8:  * logged-on user.  If the user is logged on more than once, the tty
                      9:  * returned is the one that has been used most recently.  If the user is
                     10:  * not presently logged on, the null string is returned.  Each call to
                     11:  * findtty returns a pointer to the same data area, so the string must
                     12:  * be copied if it is to be used again.
                     13:  *
                     14:  * NOTE: if this code is compiled with the "-DMAIN" option, then a main
                     15:  * program will be produced, instead of a function.  The main program
                     16:  * takes one user name as argument and outputs the ttyname on standard
                     17:  * output.
                     18:  *
                     19:  * J. Leth, IH 6E-318, x6133.
                     20:  */
                     21: 
                     22: #define NAMELEN        8
                     23:        /* Max. number of characters in a login name */
                     24: #define TTYLEN 8
                     25:        /* Max. number of characters in a tty name */
                     26: 
                     27: #ifndef MAIN
                     28: char *
                     29: findtty(user)
                     30:        char *user;     /* user login name */
                     31: {
                     32: 
                     33: #else
                     34: main(argc, argv)
                     35:        int argc;
                     36:        char *argv[];
                     37: {
                     38:        char *user;
                     39: #endif
                     40: 
                     41:        extern long ftime();
                     42:        extern int strcmp();
                     43: 
                     44:        FILE *f;
                     45:        struct utmp buf;
                     46:        long ttytime = 0L;
                     47:                /* Holds latest access time found for requested user */
                     48:        static char ttyname[TTYLEN+1];
                     49:                /* Holds name of tty with that access time */
                     50:        long acc_time = 0L;
                     51:                /* Access time of tty currently being considered */
                     52:        char *utmp = "/etc/utmp";
                     53: 
                     54:        if((f=fopen(utmp,"r"))==NULL) {
                     55:                errexit("findtty: can't open %s file.\n", utmp);
                     56:        }
                     57: 
                     58:        ttyname[0] = NUL;
                     59: 
                     60: #ifdef MAIN
                     61:        if (argc != 2) {
                     62:                usage("Usage:\tfindtty <login-id>\n\
                     63:        Outputs the name of the most recently-used terminal on which\n\
                     64:        user <login-id> is currently logged in.\n");
                     65:        }
                     66: 
                     67:        user = argv[1];
                     68: #endif
                     69: 
                     70:        while(fread(&buf,sizeof(buf),1,f) == 1) {
                     71:                /* Search utmp file for logins of the designated user.
                     72:                 * For each one found, see if the access time is later
                     73:                 * than the latest one so far; if it is, remember the
                     74:                 * ttyname and ttytime.
                     75:                 */
                     76: 
                     77:                if(strncmp(buf.ut_name, user, NAMELEN) != 0)    continue;
                     78: 
                     79:                if((acc_time=ftime(buf.ut_line)) > ttytime) {
                     80:                        ttytime = acc_time;
                     81:                        strncpy(ttyname, buf.ut_line, TTYLEN);
                     82:                        ttyname[TTYLEN] = '\0';
                     83:                                /* just to be sure string is terminated */
                     84:                }
                     85:        }
                     86: #ifndef MAIN
                     87:        return(ttyname);
                     88: #else
                     89:        printf("%s\n", ttyname);
                     90: #endif
                     91: }
                     92: 
                     93: long
                     94: ftime(s)
                     95: char *s;
                     96: {
                     97:        /* Returns the time of last access for the named device.
                     98:         * The name given as taken as the last component of the device
                     99:         * pathname.  The first component, "/dev/" is supplied by this
                    100:         * routine.  If the device doesn't exist, -1L is returned.
                    101:         */
                    102: 
                    103:        char dev[20];
                    104:        struct stat statb;
                    105: 
                    106:        strcpy(dev,"/dev/");
                    107:        strcat(dev,s);
                    108:        if( stat(dev,&statb)<0 )
                    109:                return(-1L);
                    110:        return( statb.st_atime );
                    111: }

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