Linux Ask! is a Q & A web site specific for Linux related questions. Questions are collected, answered and audited by experienced Linux users.
Spying on the physical console
Answer:
When you connect to your remote Linux server using SSH, sometimes you would like to see the message that appear in the console, you can view using the following method:
# tail -f /dev/vcs1
Where vcs1 means the virtual terminal 1, possible options are 1, 2, 3, 4 etc.
The method will save you many time from always need to visit the physical server.
Wrap each line to fit in specified width
Answer:
If you want to format a text file into a specific width, you can use the fold command
E.g.
# fold -w 40 test.txt
The above command will wrap the text file and print to standard out, with width = 40 characters.
Create temporary table in MySQL
Answer:
Temporary table is very useful when you need some tables for temporary storage, and they will be automatically removed when you disconnect from the MySQL server.
Steps:
1. Create a temporary table
mysql> CREATE TEMPORARY TABLE test (id int); 2. Insert some values
mysql> INSERT INTO test VALUES (1);
Query OK, 1 row affected (0.00 sec)
mysql> INSERT INTO test VALUES (2);
Query OK, 1 row affected (0.00 sec)
3. Query the table
mysql> SELECT * FROM test
+------+
| id |
+------+
| 1 |
| 2 |
+------+
2 rows in set (0.00 sec)
4. Close the connection and the table will be automatically removed.
How to connect MySQL without using password
Answer:
1. Create a .my.cnf in your home folder
# vi ~/.my.cnf
2. Enter your MySQL login information and save the file.
[client]
user=john
password=john_password
3. Try typing mysql in shell and you should able to login automatically.
Extract column data using awk
Answer:
A simple awk command print the 1st column of top command
# top -bc -n1 | awk '{print $1}'
If you want to specify the field separator, you can do the following
# awk -F':' '{print $1}' /etc/passwdWhich print the 1st column of file /etc/password, as if they are split by :
