lib/other/getpwent.c

   1 /*      getpwent(), getpwuid(), getpwnam() - password file routines
   2  *
   3  *                                                      Author: Kees J. Bot
   4  *                                                              31 Jan 1994
   5  */
   6 #define nil 0
   7 #define open _open
   8 #define fcntl _fcntl
   9 #define read _read
  10 #define close _close
  11 #include <sys/types.h>
  12 #include <pwd.h>
  13 #include <string.h>
  14 #include <stdlib.h>
  15 #include <unistd.h>
  16 #include <fcntl.h>
  17
  18 #define arraysize(a)    (sizeof(a) / sizeof((a)[0]))
  19 #define arraylimit(a)   ((a) + arraysize(a))
  20
  21 static char PASSWD[]= "/etc/passwd";    /* The password file. */
  22 static const char *pwfile;              /* Current password file. */
  23
  24 static char buf[1024];                  /* Read buffer. */
  25 static char pwline[256];                /* One line from the password file. */
  26 static struct passwd entry;             /* Entry to fill and return. */
  27 static int pwfd= -1;                    /* Filedescriptor to the file. */
  28 static char *bufptr;                    /* Place in buf. */
  29 static ssize_t buflen= 0;               /* Remaining characters in buf. */
  30 static char *lineptr;                   /* Place in the line. */
  31
  32 void endpwent(void)
  33 /* Close the password file. */
  34 {
  35         if (pwfd >= 0) {
  36                 (void) close(pwfd);
  37                 pwfd= -1;
  38                 buflen= 0;
  39         }
  40 }
  41
  42 int setpwent(void)
  43 /* Open the password file. */
  44 {
  45         if (pwfd >= 0) endpwent();
  46
  47         if (pwfile == nil) pwfile= PASSWD;
  48
  49         if ((pwfd= open(pwfile, O_RDONLY)) < 0) return -1;
  50         (void) fcntl(pwfd, F_SETFD, fcntl(pwfd, F_GETFD) | FD_CLOEXEC);
  51         return 0;
  52 }
  53
  54 void setpwfile(const char *file)
  55 /* Prepare for reading an alternate password file. */
  56 {
  57         endpwent();
  58         pwfile= file;
  59 }
  60
  61 static int getline(void)
  62 /* Get one line from the password file, return 0 if bad or EOF. */
  63 {
  64         lineptr= pwline;
  65
  66         do {
  67                 if (buflen == 0) {
  68                         if ((buflen= read(pwfd, buf, sizeof(buf))) <= 0)
  69                                 return 0;
  70                         bufptr= buf;
  71                 }
  72
  73                 if (lineptr == arraylimit(pwline)) return 0;
  74                 buflen--;
  75         } while ((*lineptr++ = *bufptr++) != '\n');
  76
  77         lineptr= pwline;
  78         return 1;
  79 }
  80
  81 static char *scan_colon(void)
  82 /* Scan for a field separator in a line, return the start of the field. */
  83 {
  84         char *field= lineptr;
  85         char *last;
  86
  87         for (;;) {
  88                 last= lineptr;
  89                 if (*lineptr == 0) return nil;
  90                 if (*lineptr == '\n') break;
  91                 if (*lineptr++ == ':') break;
  92         }
  93         *last= 0;
  94         return field;
  95 }
  96
  97 struct passwd *getpwent(void)
  98 /* Read one entry from the password file. */
  99 {
 100         char *p;
 101
 102         /* Open the file if not yet open. */
 103         if (pwfd < 0 && setpwent() < 0) return nil;
 104
 105         /* Until a good line is read. */
 106         for (;;) {
 107                 if (!getline()) return nil;     /* EOF or corrupt. */
 108
 109                 if ((entry.pw_name= scan_colon()) == nil) continue;
 110                 if ((entry.pw_passwd= scan_colon()) == nil) continue;
 111                 if ((p= scan_colon()) == nil) continue;
 112                 entry.pw_uid= strtol(p, nil, 0);
 113                 if ((p= scan_colon()) == nil) continue;
 114                 entry.pw_gid= strtol(p, nil, 0);
 115                 if ((entry.pw_gecos= scan_colon()) == nil) continue;
 116                 if ((entry.pw_dir= scan_colon()) == nil) continue;
 117                 if ((entry.pw_shell= scan_colon()) == nil) continue;
 118
 119                 if (*lineptr == 0) return &entry;
 120         }
 121 }
 122
 123 struct passwd *getpwuid(_mnx_Uid_t uid)
 124 /* Return the password file entry belonging to the user-id. */
 125 {
 126         struct passwd *pw;
 127
 128         endpwent();
 129         while ((pw= getpwent()) != nil && pw->pw_uid != uid) {}
 130         endpwent();
 131         return pw;
 132 }
 133
 134 struct passwd *getpwnam(const char *name)
 135 /* Return the password file entry belonging to the user name. */
 136 {
 137         struct passwd *pw;
 138
 139         endpwent();
 140         while ((pw= getpwent()) != nil && strcmp(pw->pw_name, name) != 0) {}
 141         endpwent();
 142         return pw;
 143 }