Commands | Linux Ask!

Find out which programs are listening TCP port

Mar 252010

Find out which programs are listening TCP port

Answer:

Use the command: netstat -tlnp

# netstat -tlnp

(Not all processes could be identified, non-owned process info
 will not be shown, you would have to be root to see it all.)
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State
tcp        0      0 0.0.0.0:25              0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:443             0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN

Save a file in vim without the needed permissions

Commands No Responses »

Mar 182010

Save a file in vim without the needed permissions

Answer:

Very often, you opened a file using vim, edited it and find out that the file is opened as read only, i.e. you don't have permission to make any change(s).

What will you do? Simplest method is to save it into a temp file and rename it afterward.

However, there exist a simple method that allow you to save the file anyway.

Instead of using :wq, you enter the following.

:w !sudo tee %

That is what you need.

How to execute prorgam in the current directory

Commands No Responses »

Mar 152010

How to execute prorgam in the current directory

Answer:

1. Make sure the program is executable

# chmod a+x my_program

2. Run it by appending ./ in the front of file name

# ./my_program

./ is needed if the current directory is not in your current search path (PATH)

Quickly open to file and position a cursor with vim

Commands No Responses »

Mar 092010

Quickly open to file and position a cursor with vim

Answer:

To open a file and automatically move the cursor to a particular line number

# vi +80 test.txt

The vim will move the cursor to line 80 when opened the file.

Count the number of matching lines from grep

Commands No Responses »

Mar 082010

Count the number of matching lines from grep

Answer:

grep command is useful for searching file's content by a key string, e.g.

# grep foo text.txt

All the lines matching foo will be printed.

However, to only print the number of matching lines, you can use the -c flag

# grep -c foo text.txt
4

There are total 4 lines match the word foo.

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