The sum utility calculates and prints a 16-bit checksum for the named file and the number of 512-byte blocks in the file. It is typically used to look for bad spots, or to validate a file communicated over some transmission line.

The following options are supported:

-r

Use an alternate (machine-dependent) algorithm in computing the checksum.

The following operands are supported:

file

A path name of a file. If no files are named, the standard input is used.

See largefile(5) for the description of the behavior of sum when encountering files greater than or equal to 2 Gbyte ( 2³¹ bytes).

See environ(5) for descriptions of the following environment variables that affect the execution of sum: LC_CTYPE, LC_MESSAGES, and NLSPATH.

The following exit values are returned.

0

Successful completion.

>0

An error occurred.

See attributes(5) for descriptions of the following attributes:

cksum(1), sum(1B), wc(1), attributes(5), environ(5), largefile(5)

"Read error" is indistinguishable from end of file on most devices; check the block count.

Portable applications should use cksum(1).

sum and usr/ucb/sum (see sum(1B)) return different checksums.