\fBpwck\fR verifies the integrity of the system authentication information\&. All entries in the \fI/etc/passwd\fR and \fI/etc/shadow\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\&.
.PP
Checks are made to verify that each entry has:
.TP3
\(bu
the correct number of fields
.TP
\(bu
a unique user name
.TP
\(bu
a valid user and group identifier
.TP
\(bu
a valid primary group
.TP
\(bu
a valid home directory
.TP
\(bu
a valid login shell
.LP
.PP
The checks for correct number of fields and unique user 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 user name is prompted for deletion, but the remaining checks will still be made\&. All other errors are warning and the user is encouraged to run the \fBusermod\fR command to correct the error\&.
.PP
The commands which operate on the \fI/etc/passwd\fR file are not able to alter corrupted or duplicated entries\&. \fBpwck\fR should be used in those circumstances to remove the offending entry\&.
.SH"OPTIONS"
.PP
By default, \fBpwck\fR operates on the files \fI/etc/passwd\fR and \fI/etc/shadow\fR\&. The user may select alternate files with the \fIpasswd\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\&. \fBpwck\fR can also sort entries in \fI/etc/passwd\fR and \fI/etc/shadow\fR by UID\&. To run it in sort mode pass it \fB\-s\fR flag\&. No checks are performed then, it just sorts\&.
