How to write Control Character in Unix File

Open File in vi editor
Come in Insert mode by pressing Esc i
Press Control V
Then Press Control M
Then Esc

List of Ctrl Chars
 

Numeric Values	Decimal Hex	ASCII Character	Meaning	Keyboard Entry
0	00	NUL	Null	Ctrl-@
1	01	SOH	Start of heading	Ctrl-A
2	02	STX	Start of text	Ctrl-B
3	03	ETX	Break/end of text	Ctrl-C
4	04	EOT	End of transmission	Ctrl-D
5	05	ENQ	Enquiry	Ctrl-E
6	06	ACK	Positive acknowledgment	Ctrl-F
7	07	BEL	Bell	Ctrl-G
8	08	BS	Backspace	Ctrl-H
9	09	HT	Horizontal tab	Ctrl-I
10	0A	LF	Line feed	Ctrl-J
11	0B	VT	Vertical tab	Ctrl-K
12	0C	FF	Form feed	Ctrl-L
13	0D	CR	Carriage return (Equivilant to the Enter or Return key)	Ctrl-M
14	0E	SO	Shift out	Ctrl-N
15	0F	SI	Shift in/XON (resume output)	Ctrl-O
16	10	DLE	Data link escape	Ctrl-P
17	11	DC1	Device control character 1	Ctrl-Q
18	12	DC2	Device control character 2	Ctrl-R
19	13	DC3	Device control character 3	Ctrl-S
20	14	DC4	Device control character 4	Ctrl-T
21	15	NAK	Negative acknowledgment	Ctrl-U
22	16	SYN	Synchronous idle	Ctrl-V
23	17	ETB	End of transmission block	Ctrl-W
24	18	CAN	Cancel	Ctrl-X
25	19	EM	End of medium	Ctrl-Y
26	1A	SUB	Substitute/end of file	Ctrl-Z
27	1B	ESC	Escape	Ctrl-[
28	1C	FS	File separator	Ctrl-\
29	1D	GS	Group separator	Ctrl-]
30	1E	RS	Record separator	Ctrl-^
31	1F	US	Unit separator	Ctrl-_

Secure SSH, CVS, SCP without Password Prompt

1. Suppose the domain name of your server is server, and your login name loginname.
2. On the client, generate a public and private key.
   
   

   ssh-keygen -C loginname@server -t dsa

   When asked for a password, simply press return. 
   The private key is stored in ~/.ssh/id_dsa, and the public key in ~/.ssh/id_dsa.pub.
   Never give the private key away! 

3. Copy the public file to the server with
   
   

   scp ~/.ssh/id_dsa.pub loginname@server:~/

4. Login on the server with 
   
   

   ssh loginname@server

   append the copied file to ~/.ssh/authorized_keys with

   cat ~/id_dsa.pub >>~/.ssh/authorized_keys

5. If you want to enable this features on other servers, just repeat step 3 on each of the servers.
   
   
   That’s it! If you have done everything correctly, the next time you login via SSH or use CVS over SSH, you will not need to enter a password yet you have a secure connenction.
   
   In case this does not work check /var/log/auth.log or /var/log/secure for error on server machine. If you see
   
   

   Authentication refused: bad ownership or modes for directory /home/dave/.ssh

   This is bcoz of bad permission these can be fixed with below commands.

   chmod g-w /home/your_user
   chmod 700 /home/your_user/.ssh
   chmod 600 /home/your_user/.ssh/authorized_keys

   
   

Commands will let you determine which version(s) of GCC were used to compile and link a binary executable file

his trick will let you determine which version(s) of GCC were used to compile and link a binary executable file:

Code:

strings -a /path/to/binary-file | grep "GCC:" | sort -u

Here is a dirt-simple scripted version of the pipeline.

which-gcc:

#!/bin/bash if [ -z "$1" ] ; then echo "Usage: which-gcc file" echo "Determines GCC version(s) used to build file" exit fi strings -a $1 | grep "GCC:" | sort -u

Here are some examples from my system:

Code:

$ which-gcc /bin/bash GCC: (GNU) 3.4.6 (Gentoo 3.4.6-r1, ssp-3.4.5-1.0, pie-8.7.9)

I'm using GCC 3.4.6.

Code:

$ which-gcc `which vuescan` GCC: (GNU) 3.2.2 20030222 (Red Hat Linux 3.2.2-5)

This commercial product was built on a Red Hat system, quite some time ago.

Code:

$ which-gcc /opt/google-earth/googleearth-bin GCC: (GNU) 3.4.5 20050809 (prerelease) (Ubuntu 3.4.4-6ubuntu8) GCC: (GNU) 4.0.2

The multiple version lines suggest Google Earth is at least in part statically linked. The final executable and at least one component library were built with different versions of GCC.

Code:

$ which-gcc /usr/bin/ooffice2

ooffice2 is not a GCC executable, thus no output. (It's a Bourne shell script. Reader exercise: produce a useful message when the file argument is not a GCC-created executable. )