Errno (3perl)        - System errno constants
clnt_perrno (3)      - library routines for remote procedure calls
clnt_sperrno (3)     - library routines for remote procedure calls
errno (3)            - number of last error
h_errno (3)          - get network host entry
jbd2_journal_errno (9) - returns the journal's error state.
jbd2_journal_update_sb_errno (9) - Update error in the journal.