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Introduction
Head : is built in command on unix systems or unix-like operating systems Like :
- 386BSD.
- Arch Linux.
- AIX.
- Android.
- BSD NET/2.
- Debian.
- DragonFly BSD.
- GNU Hurd.
Usage : used to display the top lines or bytes of the text files or the beginning of piped data.
How to use it ?
- You can use it to display the beginning of large text file Like : systems log .
- It can read top 10 lines by default :
head /var/log/user.log
- Or you can specify the number of lines that you need to display it.
head -n 2 /var/log/user.log
head --lines=2 /var/log/user.log
Hint : –lines= number of lines === -n number of lines
OUTPUT:
root@unixcop:~# head --lines=2 /var/log/user.log
Sep 28 15:59:47 unixcop vmnet-natd: RTM_NEWLINK: name:eth0 index:2 flags:0x00001003
Sep 28 15:59:47 unixcop vmnet-natd: RTM_NEWLINK: name:wlan0 index:3 flags:0x00011043
root@unixcop:~#
- You can either display bytes from text file
- bytes mean one character .. i will create text file with 10 char
echo "CharNum8--" > ~/bytes.txt
- Then i will display the first 8 char using head
head -c 8 ~/bytes.txt
head --bytes=8 ~/bytes.txt
OUTPUT:
CharNum8
- You can use head to read from many different files
- I can use this option for comparison.
head -q unix.txt cop.txt
head --quiet unix.txt cop.txt
![](http://unixcop.com/wp-content/uploads/2021/10/comp.txt.png)
- I can use head with option verbose to display the content of files with name of the file above
head -v unix.txt
head --verbose unix.txt
OUTPUT:
==> unix.txt <==
Name Email
Mostafa [email protected]
I will merge between verbose option and quiet option to clarify the usage of them
OUTPUT:
root@unixcop:~# head --quiet --verbose unix.txt cop.txt
==> unix.txt <==
Name Email
Mostafa [email protected]
==> cop.txt <==
Name Email
Mostafa [email protected]
root@unixcop:~#
- I can use it with pipeline
cat /var/log/user.log | head -n 3
ls -lah /root | head -n 5
- Here I can use head to store the result of command in text file
cat /var/log/user.log | head -n 3 > output.txt
OUTPUT:
root@unixcop:~# cat /var/log/user.log | head -n 3 > output.txt
root@unixcop:~# cat output.txt
Sep 28 15:59:47 unixcop vmnet-natd: RTM_NEWLINK: name:eth0 index:2 flags:0x00001003
Sep 28 15:59:47 unixcop vmnet-natd: RTM_NEWLINK: name:wlan0 index:3 flags:0x00011043
Sep 28 15:59:47 unixcop vmnet-natd: RTM_NEWROUTE: index:3
root@unixcop:~#
- You can know the head version by typing :
head --version
- For more help you can use this option:
head --help
Conclusion:
This article clarify how to use head command with practical examples.
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