In Linux, you can use command-line tools like ls, stat, and du to display information about files and directories, such as their sizes. While ls and stat provide general information, du is a specialized tool for displaying size-related details.

Use du to identify large files or folders on your system, which can help you free up storage by deleting unnecessary items. However, du isn't intended for viewing overall disk usage information.

Steps to check file and folder sizes in Linux:

  1. Check a file's size.
    $ du Documents/random.txt 
    16	Documents/random.txt

    Default size unit is in 1K block.

  2. Display file sizes in a human-readable format.
    $ du -h Documents/random.txt 
    16K	Documents/random.txt

    Size will automatically be displayed in K (Kilobytes), M (Megabytes), G (Gigabytes) or T (Terabytes) unit.

  3. Show sizes of all folders within a directory recursively.
    $ du -h Documents/
    21M	Documents/Finance
    4.0K	Documents/Secret/Empty
    40K	Documents/Secret
    21M	Documents/
  4. Set a depth level for displaying recursive folder sizes.
    $ du -h --max-depth=1 Documents/
    21M	Documents/Finance
    40K	Documents/Secret
    21M	Documents/
  5. Show folder sizes, including the total size.
    $ du -hc Documents/
    21M	Documents/Finance
    4.0K	Documents/Secret/Empty
    40K	Documents/Secret
    21M	Documents/
    21M	total
  6. Display the total size of folders or directories.
    $ du -hs Documents/
    21M	Documents/
  7. Check system folder sizes using sudo for elevated permissions.
    $ sudo du -hs /var/cache/
    [sudo] password for user: 
    117M	/var/cache/
  8. Show non-recursive directory sizes using a wildcard.
    $ sudo du -hs /var/cache/*
    6.2M	/var/cache/apparmor
    16M	/var/cache/app-info
    75M	/var/cache/apt
    6.1M	/var/cache/cracklib
    32K	/var/cache/cups
    5.2M	/var/cache/debconf
    40K	/var/cache/dictionaries-common
    2.7M	/var/cache/fontconfig
    2.1M	/var/cache/fwupd
    0	/var/cache/fwupdmgr
    60K	/var/cache/ldconfig
    2.1M	/var/cache/man
    8.0K	/var/cache/PackageKit
    8.0K	/var/cache/private
    4.0K	/var/cache/realmd
    2.2M	/var/cache/snapd
  9. Utilize the du command with additional options to explore file and directory sizes in Linux.
    $ du --help
    Usage: du [OPTION]... [FILE]...
      or:  du [OPTION]... --files0-from=F
    Summarize disk usage of the set of FILEs, recursively for directories.
    
    Mandatory arguments to long options are mandatory for short options too.
      -0, --null            end each output line with NUL, not newline
      -a, --all             write counts for all files, not just directories
          --apparent-size   print apparent sizes, rather than disk usage; although
                              the apparent size is usually smaller, it may be
                              larger due to holes in ('sparse') files, internal
                              fragmentation, indirect blocks, and the like
      -B, --block-size=SIZE  scale sizes by SIZE before printing them; e.g.,
                               '-BM' prints sizes in units of 1,048,576 bytes;
                               see SIZE format below
      -b, --bytes           equivalent to '--apparent-size --block-size=1'
      -c, --total           produce a grand total
      -D, --dereference-args  dereference only symlinks that are listed on the
                              command line
      -d, --max-depth=N     print the total for a directory (or file, with --all)
                              only if it is N or fewer levels below the command
                              line argument;  --max-depth=0 is the same as
                              --summarize
          --files0-from=F   summarize disk usage of the
                              NUL-terminated file names specified in file F;
                              if F is -, then read names from standard input
      -H                    equivalent to --dereference-args (-D)
      -h, --human-readable  print sizes in human readable format (e.g., 1K 234M 2G)
          --inodes          list inode usage information instead of block usage
      -k                    like --block-size=1K
      -L, --dereference     dereference all symbolic links
      -l, --count-links     count sizes many times if hard linked
      -m                    like --block-size=1M
      -P, --no-dereference  don't follow any symbolic links (this is the default)
      -S, --separate-dirs   for directories do not include size of subdirectories
          --si              like -h, but use powers of 1000 not 1024
      -s, --summarize       display only a total for each argument
      -t, --threshold=SIZE  exclude entries smaller than SIZE if positive,
                              or entries greater than SIZE if negative
          --time            show time of the last modification of any file in the
                              directory, or any of its subdirectories
          --time=WORD       show time as WORD instead of modification time:
                              atime, access, use, ctime or status
          --time-style=STYLE  show times using STYLE, which can be:
                                full-iso, long-iso, iso, or +FORMAT;
                                FORMAT is interpreted like in 'date'
      -X, --exclude-from=FILE  exclude files that match any pattern in FILE
          --exclude=PATTERN    exclude files that match PATTERN
      -x, --one-file-system    skip directories on different file systems
          --help     display this help and exit
          --version  output version information and exit
    
    Display values are in units of the first available SIZE from --block-size,
    and the DU_BLOCK_SIZE, BLOCK_SIZE and BLOCKSIZE environment variables.
    Otherwise, units default to 1024 bytes (or 512 if POSIXLY_CORRECT is set).
    
    The SIZE argument is an integer and optional unit (example: 10K is 10*1024).
    Units are K,M,G,T,P,E,Z,Y (powers of 1024) or KB,MB,... (powers of 1000).
    Binary prefixes can be used, too: KiB=K, MiB=M, and so on.
    
    GNU coreutils online help: <https://www.gnu.org/software/coreutils/>
    Full documentation <https://www.gnu.org/software/coreutils/du>
    or available locally via: info '(coreutils) du invocation'

    Related: du man page

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