Master Essential Linux File Viewing Commands: cat, tac, nl, more, less, head & tail

cat

Displays the contents of a file starting from the first line. cat [-AbEnTv] Key options: -A: combines -vET to show non‑printing characters. -b: numbers non‑blank lines only. -E: shows a $ at line ends. -n: numbers all lines, including blanks. -T: displays tabs as ^I. -v: makes other non‑printing characters visible.

[root@www ~]# cat /etc/issue
CentOS release 6.4 (Final)
Kernel \r on an \m

tac

Outputs a file in reverse order, starting from the last line.

tac /etc/issue

Kernel \r on an \m
CentOS release 6.4 (Final)

nl

Numbers the lines of a file. nl [-bnw] file Important options: -b a: number all lines (like cat -n). -b t: omit numbers for blank lines (default). -n ln: left‑justify numbers. -n rn: right‑justify numbers without leading zeros. -n rz: right‑justify numbers with leading zeros. -w: set the width of the number field.

[root@www ~]# nl /etc/issue
     1  CentOS release 6.4 (Final)
     2  Kernel \r on an \m

more

Pages through a file one screenful at a time. more /etc/man_db.config During a more session you can use:

Space: advance one page.

Enter: advance one line. /string: search forward for string. :f: display the current filename and line number. q: quit. b or Ctrl‑b: go back one page (works only on regular files).

less

Similar to more but provides richer navigation. less /etc/man.config Key commands while less is running:

Space or PageDown: forward one page. PageUp: backward one page. /string: search forward for string. ?string: search backward for string. n: repeat the previous forward search. N: repeat the previous search in the opposite direction. q: quit less.

head

Shows the first few lines of a file. head [-n number] file Option: -n number : display the specified number of lines (default is 10).

[root@www ~]# head /etc/man.config

[root@www ~]# head -n 20 /etc/man.config

tail

Shows the last few lines of a file. tail [-n number] file Options: -n number : display the specified number of lines from the end (default is 10). -f: follow the file as it grows; stop with Ctrl‑c.

[root@www ~]# tail /etc/man.config
# (shows last 10 lines)
[root@www ~]# tail -n 20 /etc/man.config