.TH SUM 1 
.SH NAME
sum \- sum and count blocks in a file
.SH SYNOPSIS
.B sum
file
.SH DESCRIPTION
.I Sum
calculates and prints a 16-bit checksum for the named file,
and also prints the number of blocks in the file.
It is typically used to look for bad spots, or
to validate a file communicated over
some transmission line.
.SH "SEE ALSO"
ckdir(1), wc(1)
.SH DIAGNOSTICS
`Read error'
is indistinuishable from end of file on
most devices; check the block count.