COHERENT manpages
This page displays the COHERENT manpage for group [Define groups of users].
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group -- System Administration Define groups of users The group file /etc/group describes the user groups that have been defined on your COHERENT system. This allows users to control the access that members of their group have to certain files. /etc/group contains the information to map any ASCII group name to the corresponding numerical group identifier, and vice versa. It also contains, in ASCII, the names of the members of each group. This information is used by, among others, the command newgrp. Each group has an entry in the file /etc/group one line per entry. Each line consists of four colon-separated ASCII fields, as follows: group_name : password : group_number : member[,member...] Passwords are encrypted with crypt, so the group file is generally readable. The COHERENT system has five system calls that manipulate /etc/group, as follows: endgrent() Close /etc/group. getgrent() Return the next entry from /etc/group. getgrnam() Return the first entry with a given group name. getgrgid() Return the first entry with a given group identifier. setgrent() Rewind /etc/group, so that searches can begin again from the beginning of the file. The calls getgrent(), getgrid(), and getgrnam() each return a pointer to structure group, which the header file grp.h defines as follows: struct group { char *gr_name; /* Group name */ char *gr_passwd;/* Group password */ int gr_gid; /* Numeric group id */ char **gr_mem; /* Group members */ }; A user can belong to more than one group. His ``main'' group, however, is the one that is named is in his entry in the file /etc/passwd. When a user creates a file, that file by default is ``owned'' by the user's main group. For example, consider user joe, who has the following entry in /etc/passwd: joe:*:10:5:Joe Smith:/usr/joe:/usr/bin/ksh The fourth field, which in this example has the value 5, gives the number of the user's main group. (For details on what the other fields mean, see the Lexicon entry for passwd.) Looking in /etc/group, we see the following entry for group 5: user::5: Thus, whenever joe creates a file, by default it will be ``owned'' by group user. Any member of group user will be granted that file's group-level permissions on that file. A user can use the command chmod to change the group-level permissions on any file he owns. The superuser root can use the command chgrp to changes the group ownership for any file. For details on how to use these commands, see their entries in the Lexicon. Files /etc/group See Also Administering COHERENT, chgrp(), chmod, chown, endgrent(), getgrent(), getgrgid(), getgrnam(), grp.h, newgrp, passwd, setgrend() Notes At present the group password field cannot be set directly (no command similar to passwd exists for groups). One alternative is to set the password in the /etc/passwd file for a user with the passwd command, then transcribe the password into the group file manually.