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Classic Shell Scripting by Nelson H. F. Beebe, Arnold Robbins

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Filesystem Space Information

With suitable options, the find and ls commands report file sizes, so with the help of a short awk program, you can report how many bytes your files occupy:

$ find -ls | awk '{Sum += $7} END {printf("Total: %.0f bytes\n", Sum)}'
Total: 23079017 bytes

However, that report underestimates the space used, because files are allocated in fixed-size blocks, and it tells us nothing about the used and available space in the entire filesystem. Two other useful tools provide better solutions: df and du.

The df Command

df (disk free) gives a one-line summary of used and available space on each mounted filesystem. The units are system-dependent blocks on some systems, and kilobytes on others. Most modern implementations support the -k option to force kilobyte units, and the -l (lowercase L) option to include only local filesystems, excluding network-mounted ones. Here is a typical example from one of our web servers:

$ df -k
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/sda5              5036284   2135488   2644964  45% /
/dev/sda2                38890      8088     28794  22% /boot
/dev/sda3             10080520   6457072   3111380  68% /export
none                    513964         0    513964   0% /dev/shm
/dev/sda8               101089      4421     91449   5% /tmp
/dev/sda9             13432904    269600  12480948   3% /var
/dev/sda6              4032092   1683824   2143444  44% /ww

GNU df provides the -h (human-readable) option to produce a more compact, but possibly more confusing, report:

$ df -h Filesystem Size Used Avail Use% Mounted on /dev/sda5 4.9G 2.1G 2.6G 45% / /dev/sda2 38M 7.9M 29M 22% ...

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