[SOLVED] How to remove a line?

mhsahkir · 03-17-2015, 01:14 PM

when i insert a line using command echo"" how can i remove that line? thanks advance.

[root@jakir ~]# echo "first inserting line" >file3
[root@jakir ~]# echo "first inserting line" >file3
[root@jakir ~]# cat file3
first inserting line
[root@jakir ~]# echo "first inserting line" >>file3
[root@jakir ~]# echo "first inserting line" >>file3
[root@jakir ~]# echo "first inserting line" >>file3
[root@jakir ~]# cat file3
first inserting line
first inserting line
first inserting line
first inserting line
[root@jakir ~]# rm -r "first inserting line"
rm: cannot remove `first inserting line': No such file or directory
[root@jakir ~]# ^C
[root@jakir ~]# vi file3
[root@jakir ~]# cat file3

first inserting line
first inserting line

GNU/Linux · 03-17-2015, 01:56 PM

First thing first, if you really want to mess around please do it using a normal user not as root.

Quote:

rm -r "first inserting line"

'rm -r' will delete directories recursively and that's very dangerous. rm takes filename or directory name as it's argument not contents of a text file. see 'man rm'

Now you need to know about redirection. Check out bash and sed, more specifically 'sed' for your line deletion task but it's really recommended that you get your hands dirty learning bash first.

onebuck · 03-17-2015, 04:00 PM

Hi,

I too agree that you should use 'root' carefully. A newbie can do major damage with just one slip. Especially when you are using 'rm -r' on something. 'man rm';

Quote:

NAME

rm - remove files or directories SYNOPSIS

rm [OPTION]... FILE... DESCRIPTION

This manual page documents the GNU version of rm. rm removes each specified file. By default, it does not remove directories. If a file is unwritable, the standard input is a tty, and the -f or --force option is not given, rm prompts the user for whether to remove the file. If the response does not begin with `y' or `Y', the file is skipped.

OPTIONS

Remove (unlink) the FILE(s).
-d, --directory unlink FILE, even if it is a non-empty directory (super-user only)
-f, --force ignore nonexistent files, never prompt
-i, --interactive prompt before any removal
-r, -R, --recursive remove the contents of directories recursively
-v, --verbose explain what is being done
--help display this help and exit
--version output version information and exit
To remove a file whose name starts with a `-', for example `-foo', use one of these commands:
rm -- -foo
rm ./-foo Note that if you use rm to remove a file, it is usually possible to
recover the contents of that file. If you want more assurance that the
contents are truly unrecoverable, consider using shred.

You should get in the habit of using the 'man command'.

Quote:

Just a few links to aid you to gaining some understanding;

  1 Linux Documentation Project 
2 Rute Tutorial & Exposition 
3 Linux Command Guide  
4 Bash Beginners Guide 
5 Bash Reference Manual 
6 Advanced Bash-Scripting Guide 
7 Linux Newbie Admin Guide 
8 LinuxSelfHelp 
9 Utimate Linux Newbie Guide

The above links and others can be found at 'Slackware-Links'. More than just Slackware® links!

Hope this helps.
Have fun & enjoy!

joe_2000 · 03-17-2015, 04:36 PM

Something to play with and analyse in combination with man pages:

Code:

user@localhost:~/tmp$ echo line 1 >> testfile
user@localhost:~/tmp$ echo line 2 >> testfile
user@localhost:~/tmp$ echo line 3 >> testfile
user@localhost:~/tmp$ echo line 4 >> testfile
user@localhost:~/tmp$ echo line 5 >> testfile
user@localhost:~/tmp$ head -n -1 testfile 
line 1
line 2
line 3
line 4
user@localhost:~/tmp$ head -n -1 testfile > testfile_without_last_line
user@localhost:~/tmp$ cat testfile_without_last_line 
line 1
line 2
line 3
line 4

mhsahkir · 03-18-2015, 05:27 PM

ok thats cool idea,next time i will be work as regular user.

Keith Hedger · 03-19-2015, 07:02 AM

Use sed like so:

Code:

sed '2d' /path/to/file

Removes line 2
Or to remove a range of lines

Code:

sed '2,4d' /path/to/file

Removes lines 2-4 inclusive.