\fBgrpck\fR verifies the integrity of the system authentication information\&. All entries in the \fI/etc/group\fR and \fI/etc/gshadow\fR are checked to see that the entry has the proper format and valid data in each field\&. The user is prompted to delete entries that are improperly formatted or which have other uncorrectable errors\&.
The checks for correct number of fields and unique group name are fatal\&. If the entry has the wrong number of fields, the user will be prompted to delete the entire line\&. If the user does not answer affirmatively, all further checks are bypassed\&. An entry with a duplicated group name is prompted for deletion, but the remaining checks will still be made\&. All other errors are warnings and the user is encouraged to run the \fBgroupmod\fR command to correct the error\&.
The commands which operate on the \fI/etc/group\fR file are not able to alter corrupted or duplicated entries\&. \fBgrpck\fR should be used in those circumstances to remove the offending entry\&.
.SH"OPTIONS"
.PP
By default, \fBgrpck\fR operates on the files \fI/etc/group\fR and \fI/etc/gshadow\fR\&. The user may select alternate files with the \fIgroup\fR and \fIshadow\fR parameters\&. Additionally, the user may execute the command in read\-only mode by specifying the \fB\-r\fR flag\&. This causes all questions regarding changes to be answered \fIno\fR without user intervention\&. \fBgrpck\fR can also sort entries in \fI/etc/group\fR and \fI/etc/gshadow\fR by GID\&. To run it in sort mode pass it \fB\-s\fR flag\&. No checks are performed then, it just sorts\&.
