Proc - IO Accounting Fields

/proc/<pid>/io display the IO accounting fields, which are IO statistics for each running process.

dd if=/dev/zero of=/tmp/test.dat &
[1] 3828
 
 
cat /proc/3828/io
 
rchar: 323934931
wchar: 323929600
syscr: 632687
syscw: 632675
read_bytes: 0
write_bytes: 323932160
cancelled_write_bytes: 0

where:

WARNING: At its current implementation state, this is a bit racy on 32-bit machines: if process A reads process B's /proc/pid/io while process B is updating one of those 64-bit counters, process A could see an intermediate result.

More information about this can be found within the taskstats documentation in Documentation/accounting.