- print checksum and block count for a file
sum [-r] [file]...
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:
Use an alternate (machine-dependent) algorithm in computing the checksum.
The following operands are supported:
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.
An error occurred.
See attributes(5) for descriptions of the following attributes:
“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.