Meaning of the statement - du -sk * |sort -rn|head

Question

I am facing trouble understanding the meaning of the Linux command du -sk * |sort -rn|head. I understand that du is used to display the disk usage but I'm facing trouble understanding the rest of the command. Can somebody please breakdown what's exactly happening here? Also can some good resources be suggested for studying complex linux commands in detail?

du: Show usage for each file or directory. sort: Reverse sort in numeric order, bringing the largest ones on top. head: Show the first few. — n. m. could be an AI, Jan 04 '22 at 09:46
Can you explain with all the flags? And the intermediate steps? What happens first and how data is passed from du to sort to rn? — Dawson Smith, Jan 04 '22 at 09:48
The `|` character (called *pipe*) takes the output of the preceding command and sends it to the input of the following command. Type `man du` to read about `du` flags. — n. m. could be an AI, Jan 04 '22 at 09:53
There's a star(*) also in between. Can you explain a bit more? — Dawson Smith, Jan 04 '22 at 10:08

ceving · Accepted Answer · 2022-01-04T11:32:48.780

Good resources to study Unix commands are the manual pages.

man du:

Summarize disk usage of the set of FILEs, recursively for directories.
-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
-k     like --block-size=1K
-s, --summarize
       display only a total for each argument

man sort:

Write sorted concatenation of all FILE(s) to standard output.
-r, --reverse
       reverse the result of comparisons
-n, --numeric-sort
       compare according to string numerical value

man head:

Print  the  first  10 lines of each FILE to standard output.  With more
than one FILE, precede each with a header giving the file name.

The command shows the 10 largest directories or files.

Step by step:

#! /bin/bash

echo 'Create 20 files with random size.'
for i in {1..20}; do
  dd if=/dev/zero of="$i".data bs=1k count="$RANDOM"
done

echo 'Show the size of all 20 files in default units.'
du -s *.data

echo 'Show the size of all 20 files in KB.'
du -sk *.data

echo 'Show the size of all 20 files in KB and sort it in numeric order.'
du -sk *.data | sort -n

echo 'Show the size of all 20 files in KB and sort it in reverse numeric order.'
du -sk *.data | sort -rn

echo 'Show just the first 10 files of the previous output.'
du -sk *.data | sort -rn | head

Meaning of the statement - du -sk * |sort -rn|head

1 Answers1