CRYPT(3)                   POSIX Programmer's Manual                  CRYPT(3)



PPRROOLLOOGG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.


NNAAMMEE
       crypt -- string encoding function (CCRRYYPPTT)

SSYYNNOOPPSSIISS
       #include <unistd.h>

       char *crypt(const char *_k_e_y, const char *_s_a_l_t);

DDEESSCCRRIIPPTTIIOONN
       The _c_r_y_p_t() function is a string encoding function. The algorithm is
       implementation-defined.

       The _k_e_y argument points to a string to be encoded. The _s_a_l_t argument
       shall be a string of at least two bytes in length not including the
       null character chosen from the set:

           aa bb cc dd ee ff gg hh ii jj kk ll mm nn oo pp qq rr ss tt uu vv ww xx yy zz
           AA BB CC DD EE FF GG HH II JJ KK LL MM NN OO PP QQ RR SS TT UU VV WW XX YY ZZ
           00 11 22 33 44 55 66 77 88 99 .. //

       The first two bytes of this string may be used to perturb the encoding
       algorithm.

       The return value of _c_r_y_p_t() points to static data that is overwritten
       by each call.

       The _c_r_y_p_t() function need not be thread-safe.

RREETTUURRNN VVAALLUUEE
       Upon successful completion, _c_r_y_p_t() shall return a pointer to the
       encoded string. The first two bytes of the returned value shall be
       those of the _s_a_l_t argument. Otherwise, it shall return a null pointer
       and set _e_r_r_n_o to indicate the error.

EERRRROORRSS
       The _c_r_y_p_t() function shall fail if:

       EENNOOSSYYSS The functionality is not supported on this implementation.

       _T_h_e _f_o_l_l_o_w_i_n_g _s_e_c_t_i_o_n_s _a_r_e _i_n_f_o_r_m_a_t_i_v_e_.

EEXXAAMMPPLLEESS
   EEnnccooddiinngg PPaasssswwoorrddss
       The following example finds a user database entry matching a particular
       user name and changes the current password to a new password. The
       _c_r_y_p_t() function generates an encoded version of each password. The
       first call to _c_r_y_p_t() 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 _c_r_y_p_t() encodes the new password
       before it is stored.

       The _p_u_t_p_w_e_n_t() function, used in the following example, is not part of
       POSIX.1-2008.

           ##iinncclluuddee <<uunniissttdd..hh>>
           ##iinncclluuddee <<ppwwdd..hh>>
           ##iinncclluuddee <<ssttrriinngg..hh>>
           ##iinncclluuddee <<ssttddiioo..hh>>
           ......
           iinntt vvaalliidd__cchhaannggee;;
           iinntt ppffdd;;  //** IInntteeggeerr ffoorr ffiillee ddeessccrriippttoorr rreettuurrnneedd bbyy ooppeenn(()).. **//
           FFIILLEE **ffppffdd;;  //** FFiillee ppooiinntteerr ffoorr uussee iinn ppuuttppwweenntt(()).. **//
           ssttrruucctt ppaasssswwdd **pp;;
           cchhaarr uusseerr[[110000]];;
           cchhaarr oollddppaasssswwdd[[110000]];;
           cchhaarr nneewwppaasssswwdd[[110000]];;
           cchhaarr ssaavveeppaasssswwdd[[110000]];;
           ......
           vvaalliidd__cchhaannggee == 00;;
           wwhhiillee ((((pp == ggeettppwweenntt(()))) !!== NNUULLLL)) {{
               //** CChhaannggee eennttrryy iiff ffoouunndd.. **//
               iiff ((ssttrrccmmpp((pp-->>ppww__nnaammee,, uusseerr)) ==== 00)) {{
                   iiff ((ssttrrccmmpp((pp-->>ppww__ppaasssswwdd,, ccrryypptt((oollddppaasssswwdd,, pp-->>ppww__ppaasssswwdd)))) ==== 00)) {{
                       ssttrrccppyy((ssaavveeppaasssswwdd,, ccrryypptt((nneewwppaasssswwdd,, uusseerr))));;
                       pp-->>ppww__ppaasssswwdd == ssaavveeppaasssswwdd;;
                       vvaalliidd__cchhaannggee == 11;;
                   }}
                   eellssee {{
                       ffpprriinnttff((ssttddeerrrr,, ""OOlldd ppaasssswwoorrdd iiss nnoott vvaalliidd\\nn""));;
                   }}
               }}
               //** PPuutt ppaasssswwdd eennttrryy iinnttoo ppttmmpp.. **//
               ppuuttppwweenntt((pp,, ffppffdd));;
           }}

AAPPPPLLIICCAATTIIOONN UUSSAAGGEE
       The values returned by this function need not be portable among XSI-
       conformant systems.

RRAATTIIOONNAALLEE
       None.

FFUUTTUURREE DDIIRREECCTTIIOONNSS
       None.

SSEEEE AALLSSOO
       _e_n_c_r_y_p_t(), _s_e_t_k_e_y()

       The Base Definitions volume of POSIX.1-2008, <<uunniissttdd..hh>>

CCOOPPYYRRIIGGHHTT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
       -- Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, Copyright (C) 2013 by the Institute of
       Electrical and Electronics Engineers, Inc and The Open Group.  (This is
       POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/online.html .

       Any typographical or formatting errors that appear in this page are
       most likely to have been introduced during the conversion of the source
       files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .



IEEE/The Open Group                  2013                             CRYPT(3)
