To access password file under UNIX

In standard Unix the password file is /etc/passwd. On a Unix system with either NIS/yp or password shadowing, much of the password data may be elsewhere. An entry in the password file consists of seven colon delimited fields:
Username
Encrypted password (And optional password aging data)
User number
Group Number
GECOS Information
Home directory
Shell
]
] Sample entry from /etc/passwd:
]
] will:6gf74giE2e8fg:7516:12:Alexander:/home/fsg/will:/bin/bash
]
Broken down, this passwd file line shows:
Username: Alexander
Encrypted password: 6gf74giE2e8fg
User number: 7516
Group Number: 12
GECOS Information: Alexander
Home directory: /home/fsg/will
Shell: /bin/bash

CRACKING UNIX PASSWORD

"Unix passwords cannot be decrypted" I'm not saying it,they say.
Unix passwords are encrypted with a one way function. The login program
encrypts the text you enter at the "password:" prompt and compares
that encrypted string against the encrypted form of your password.
Password cracking software uses wordlists. Each word in the wordlist
is encrypted and the results are compared to the encrypted form of the
target password.
The best cracking program for Unix passwords is currently Crack by
Alec Muffett. For PC-DOS, the best package to use is currently
CrackerJack. CrackerJack is available via ftp from clark.net/pub/jcase/.