term% ls -F
term% cat index.txt
ICHECK(1M)                                                          ICHECK(1M)

       icheck - file system storage consistency check

       icheck [ -s ]  [ -b numbers ] [ filesystem ]

       Icheck  examines  a  file  system, builds a bit map of used blocks, and
       compares this bit map against the free list maintained on the file sys‐
       tem.   If  the file system is not specified, a set of default file sys‐
       tems is checked.  The normal output of icheck includes a report of

              The total number of files and the numbers of regular, directory,
              block special and character special files.

              The  total  number  of blocks in use and the numbers of single-,
              double-, and triple-indirect blocks and directory blocks.

              The number of free blocks.

              The number of blocks missing; i.e. not in any file  nor  in  the
              free list.

       The  -s  option causes icheck to ignore the actual free list and recon‐
       struct a new one by rewriting the super-block of the file system.   The
       file  system  should  be  dismounted while this is done; if this is not
       possible (for example if the root file system has to be salvaged)  care
       should  be  taken  that the system is quiescent and that it is rebooted
       immediately afterwards so that the old, bad in-core copy of the  super-
       block  will not continue to be used.  Notice also that the words in the
       super-block which indicate the size of the free list and of the  i-list
       are  believed.   If  the  super-block has been curdled these words will
       have to be patched.  The -s option causes the normal output reports  to
       be suppressed.

       Following the -b option is a list of block numbers; whenever any of the
       named blocks turns up in a file, a diagnostic is produced.

       Icheck is faster if the raw version of the special file is used,  since
       it reads the i-list many blocks at a time.

       Default file systems vary with installation.

       dcheck(1), ncheck(1), filsys(5), clri(1)

       For duplicate blocks and bad blocks (which lie outside the file system)
       icheck announces the difficulty, the i-number, and the  kind  of  block
       involved.   If a read error is encountered, the block number of the bad
       block is printed and icheck considers it to contain 0.  `Bad freeblock'
       means  that  a block number outside the available space was encountered
       in the free list.  `n dups in free' means that n blocks were  found  in
       the free list which duplicate blocks either in some file or in the ear‐
       lier part of the free list.

       Since icheck is inherently two-pass in nature,  extraneous  diagnostics
       may be produced if applied to active file systems.
       It  believes  even  preposterous  super-blocks and consequently can get
       core images.