The -b, -k, and -m options will force du to print the disk usage in specified units. Note that these cannot be used with the -h option:

• Print the size in bytes (by default):

        $ du -b FILE(s)

• Print the size in kilobytes:

        $ du -k FILE(s)

• Print the size in megabytes:

        $ du -m FILE(s)

• Print the size in the given BLOCK size specified:

        $ du -B BLOCK_SIZE FILE(s)

Here, BLOCK_SIZE is specified in bytes.

Note that the file size returned is not intuitively obvious. With the -b option, du reports the exact number of bytes in the file. With other options, du reports the amount of disk space used by the file. Since disk space is allocated in fixed-size chunks (commonly 4 K), the space used by a 400-byte file will be a single block (4 K):

        $ du pcpu.sh
        4  pcpu.sh
        $ du -b pcpu.sh
        439 pcpu.sh
        $ du -k pcpu.sh
        4  pcpu.sh
        $ du -m pcpu.sh
        1  pcpu.sh
        $ du -B 4 pcpu.sh
        1024  pcpu.sh