From Linuxintro

The command du allows you to find out the disk space used by a file:

# du -csh *
1.2M    CMakeFiles
4.0K    CMakeLists.txt
8.0K    CMakeTmp
4.0K    browser.cpp
4.0K    browser.h
4.0K    main.cpp
1.3M    total

The difference to ls -l is that you can get a total and that directories are also shown with the correct size.

# ls -ld CMakeFiles/
drwxr-xr-x 7 root root 4096 Feb 14 10:12 CMakeFiles/
# du -csh CMakeFiles/
1.2M    CMakeFiles/
1.2M    total

be aware

tweedleburg:~ # du -sch archiv
0       archiv
0       total
tweedleburg:~ # du -sch archiv/
80G     archiv/
80G     total
tweedleburg:~ # ll archiv
lrwxrwxrwx 1 root root 22 Jul 15 13:09 archiv -> /mnt/barracuda/archiv/

See also