username.c

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/*-------------------------------------------------------------------------
 *
 * username.c
 *    get user name
 *
 * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *    src/common/username.c
 *
 *-------------------------------------------------------------------------
 */
 
#ifndef FRONTEND
#include "postgres.h"
#else
#include "postgres_fe.h"
#endif
 
#include <pwd.h>
#include <unistd.h>
 
#include "common/username.h"
 
/*
 * Returns the current user name in a static buffer
 * On error, returns NULL and sets *errstr to point to a palloc'd message
 */
const char *
get_user_name(char **errstr)
{
#ifndef WIN32
    struct passwd *pw;
    uid_t       user_id = geteuid();
 
    *errstr = NULL;
 
    errno = 0;                  /* clear errno before call */
    pw = getpwuid(user_id);
    if (!pw)
    {
        *errstr = psprintf(_("could not look up effective user ID %ld: %s"),
                           (long) user_id,
                           errno ? strerror(errno) : _("user does not exist"));
        return NULL;
    }
 
    return pw->pw_name;
#else
    /* Microsoft recommends buffer size of UNLEN+1, where UNLEN = 256 */
    /* "static" variable remains after function exit */
    static char username[256 + 1];
    DWORD       len = sizeof(username);
 
    *errstr = NULL;
 
    if (!GetUserName(username, &len))
    {
        *errstr = psprintf(_("user name lookup failure: error code %lu"),
                           GetLastError());
        return NULL;
    }
 
    return username;
#endif
}
 
 
/*
 * Returns the current user name in a static buffer or exits
 */
const char *
get_user_name_or_exit(const char *progname)
{
    const char *user_name;
    char       *errstr;
 
    user_name = get_user_name(&errstr);
 
    if (!user_name)
    {
        fprintf(stderr, "%s: %s\n", progname, errstr);
        exit(1);
    }
    return user_name;
}