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#include <pwd.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>
#include <limits.h>
static char *copy_str(const char *src, char **buf, size_t *buflen)
{
size_t len = strlen(src) + 1;
if (len > *buflen)
return NULL;
char *dst = *buf;
memcpy(dst, src, len);
*buf += len;
*buflen -= len;
return dst;
}
int getpwuid_r(uid_t uid, struct passwd *pwd, char *buf, size_t buflen,
struct passwd **result)
{
FILE *stream = fopen("/etc/passwd", "r");
if (stream == NULL) {
*result = NULL;
return errno;
}
char line[LINE_MAX];
while (fgets(line, sizeof(line), stream)) {
char *name = strtok(line, ":");
char *passwd = strtok(NULL, ":");
char *uid_str = strtok(NULL, ":");
char *gid_str = strtok(NULL, ":");
strtok(NULL, ":");
char *dir = strtok(NULL, ":");
char *shell = strtok(NULL, "\n");
if (name == NULL || passwd == NULL || uid_str == NULL ||
gid_str == NULL)
continue;
uid_t file_uid = (uid_t)strtoul(uid_str, NULL, 10);
if (file_uid != uid)
continue;
size_t rem = buflen;
pwd->pw_name = copy_str(name, &buf, &rem);
pwd->pw_dir = copy_str(dir ? dir : "", &buf, &rem);
pwd->pw_shell = copy_str(shell ? shell : "", &buf, &rem);
pwd->pw_uid = file_uid;
pwd->pw_gid = (gid_t)strtoul(gid_str, NULL, 10);
pwd->pw_uid = file_uid;
pwd->pw_gid = (gid_t)strtoul(gid_str, NULL, 10);
if (pwd->pw_name == NULL || pwd->pw_dir == NULL ||
pwd->pw_shell == NULL) {
fclose(stream);
return ERANGE;
}
fclose(stream);
*result = pwd;
return 0;
}
fclose(stream);
*result = NULL;
return 0;
}
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