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/* utent.c <ndf@linux.mit.edu> */
/* Let it be known that this is very possibly the worst standard ever.  HP-UX
   does one thing, someone else does another, linux another... If anyone
   actually has the standard, please send it to me.

   Note that because of the way this stupid stupid standard works, you
   have to call endutent() to close the file even if you've not called
   setutent -- getutid and family use the same file descriptor. */

#include <unistd.h>
#include <fcntl.h>
#include <paths.h>
#include <errno.h>
#include <string.h>
#include <utmp.h>

static const char *ut_name = _PATH_UTMP;

static int ut_fd = -1;

struct utmp *
getutent(void)
{
    static struct utmp utmp;
    if (ut_fd == -1) {
        setutent();
        if (ut_fd == -1)
            return NULL;
    }

    if (read(ut_fd, (char *)&utmp, sizeof(struct utmp)) != sizeof(struct utmp))
        return NULL;
    return &utmp;
}

void
setutent(void)
{
    int xerrno = errno;
    if (ut_fd != -1)
        close(ut_fd); /* ... Should this be an Lseek ? */

    if ((ut_fd = open(ut_name, O_RDWR)) < 0) {
        if (errno != EACCES || (ut_fd = open(ut_name, O_RDONLY)) < 0) {
            ut_fd=-1;
        }
    }
    if (ut_fd != -1) errno = xerrno;
}

void
endutent(void)
{
    if (ut_fd != -1) {
        close(ut_fd);
        ut_fd = -1;
    }
}

struct utmp *
getutid(const struct utmp *utmp_entry)
{
    struct utmp *utmp;

    while ((utmp = getutent()) != NULL) {
        if ((utmp_entry->ut_type == RUN_LVL ||
             utmp_entry->ut_type == BOOT_TIME ||
             utmp_entry->ut_type == NEW_TIME  ||
             utmp_entry->ut_type == OLD_TIME) &&
            utmp->ut_type == utmp_entry->ut_type)
            return utmp;
        if ((utmp_entry->ut_type == INIT_PROCESS ||
             utmp_entry->ut_type == DEAD_PROCESS ||
             utmp_entry->ut_type == LOGIN_PROCESS ||
             utmp_entry->ut_type == USER_PROCESS) &&
            !strncmp(utmp->ut_id, utmp_entry->ut_id, sizeof(utmp->ut_id)))
            return utmp;
    }

    return NULL;
}

struct utmp *
getutline(const struct utmp *utmp_entry)
{
    struct utmp *utmp;

#if 0 /* This is driving me nuts.  It's not an implementation problem -
         it's a matter of how things _SHOULD_ behave.  Groan. */
    if (ut_fd!=-1)
        lseek(ut_fd, (off_t) -sizeof(struct utmp), SEEK_CUR);
#endif

    while ((utmp = getutent()) != NULL) {
        if ((utmp->ut_type == USER_PROCESS  ||
             utmp->ut_type == LOGIN_PROCESS) &&
            !strcmp(utmp->ut_line, utmp_entry->ut_line))
            return utmp;
    }

    return NULL;
}

struct utmp *
pututline(const struct utmp *utmp_entry)
{
    int xerrno = errno;

#if 0
    /* Ignore the return value.  That way, if they've already positioned
       the file pointer where they want it, everything will work out. */
    if (ut_fd != -1)
        (void) lseek(ut_fd, (off_t) -sizeof(struct utmp), SEEK_CUR);
#endif

    if (getutid(utmp_entry) != NULL)
        lseek(ut_fd, (off_t) -sizeof(struct utmp), SEEK_CUR);
    else if (ut_fd==-1)
        return NULL;
    else
        lseek(ut_fd, (off_t) 0, SEEK_END);

    /*
     * At this point I could make sure the offset we're at is an exact multiple
     * of the sizeof struct utmp. Should I? Up or down?  --RdB
     */

    if (write(ut_fd, (char *) utmp_entry, sizeof(struct utmp))
            != sizeof(struct utmp))
        return NULL;

    /* I think this final lseek gets the result Nat was after ... RdB */
    lseek(ut_fd, (off_t) -sizeof(struct utmp), SEEK_CUR);

    /* Ignoring untrapped errors */
    errno = xerrno;
    return (struct utmp *) utmp_entry;
}

void
utmpname(const char *new_ut_name)
{
    endutent();

    if (new_ut_name != NULL)
        ut_name = new_ut_name;
}
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