System data files and information of Reading Notes in UNIX advanced programming (1)

1. the UNIX system password file contains the fields shown in the passwd struct defined in <PWD. h>.

POSIX defines two functions for getting password file items. After the user login name or user ID is given. The two functions can be used to view related items.

# Include <PWD. h>

Struct passwd * getpwuid (uid_t UID );

Struct passwd * getpwnam (const char * Name );

To view the entire password file, use the following three functions:

# Include <PWD. h>

Struct passwd * getpwent (void); // return the next record in the password file

Void setpwent (void); // locate the password file to the opening

Void endpwent (void); // close the password file. After opening the password file, remember to close the password file.

2. For the sake of security, many systems store encryption passwords in a place called Shadow passwords. The fields stored in the file are as follows:

Similar to a group of functions that access the password file, another group of functions can access the shadow password file.

# Include <shadow. h>

Struct spwd * getspnam (const char * Name );

Struct spwd * getspent (void );

Void setspent (void );

Void endspent (void );

3. group files

UNIX files contain the fields shown in. These fields are also included in the group structure defined in <GRP. h>.

POSIX defines the following two functions to find information about the user group based on the user name or user ID.

# Include <GRP. h>

Struct Group * getgrgid (gid_t GID );

Struct Group * getgrnam (const char * Name );

Similar to accessing a password file. To access the entire group file, you need to use the following three functions:

# Include <GRP. h>

Struct Group * getgrent (void );

Void setgrent (void );

Void endgrent (void );

System data files and information of Reading Notes in UNIX advanced programming (1)