Originální popis anglicky:
crypt - string encoding function (
CRYPT)
Návod, kniha: POSIX Programmer's Manual
#include <unistd.h>
char *crypt(const char *
key, const char
*salt );
The
crypt() function is a string encoding function. The algorithm is
implementation-defined.
The
key argument points to a string to be encoded. The
salt
argument is a string chosen from the set:
a b c d e f g h i j k l m n o p q r s t u v w x y z
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
0 1 2 3 4 5 6 7 8 9 . /
The first two characters of this string may be used to perturb the encoding
algorithm.
The return value of
crypt() points to static data that is overwritten by
each call.
The
crypt() function need not be reentrant. A function that is not
required to be reentrant is not required to be thread-safe.
Upon successful completion,
crypt() shall return a pointer to the encoded
string. The first two characters of the returned value shall be those of the
salt argument. Otherwise, it shall return a null pointer and set
errno to indicate the error.
The
crypt() function shall fail if:
- ENOSYS
- The functionality is not supported on this implementation.
The following sections are informative.
The following example finds a user database entry matching a particular user
name and changes the current password to a new password. The
crypt()
function generates an encoded version of each password. The first call to
crypt() produces an encoded version of the old password; that encoded
password is then compared to the password stored in the user database. The
second call to
crypt() encodes the new password before it is stored.
The
putpwent() function, used in the following example, is not part of
IEEE Std 1003.1-2001.
#include <unistd.h>
#include <pwd.h>
#include <string.h>
#include <stdio.h>
...
int valid_change;
int pfd; /* Integer for file descriptor returned by open(). */
FILE *fpfd; /* File pointer for use in putpwent(). */
struct passwd *p;
char user[100];
char oldpasswd[100];
char newpasswd[100];
char savepasswd[100];
...
valid_change = 0;
while ((p = getpwent()) != NULL) {
/* Change entry if found. */
if (strcmp(p->pw_name, user) == 0) {
if (strcmp(p->pw_passwd, crypt(oldpasswd, p->pw_passwd)) == 0) {
strcpy(savepasswd, crypt(newpasswd, user));
p->pw_passwd = savepasswd;
valid_change = 1;
}
else {
fprintf(stderr, "Old password is not valid\n");
}
}
/* Put passwd entry into ptmp. */
putpwent(p, fpfd);
}
The values returned by this function need not be portable among XSI-conformant
systems.
None.
None.
encrypt() ,
setkey() , the Base Definitions volume of
IEEE Std 1003.1-2001,
<unistd.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html
.
