Linux and UNIX Man Pages

Linux & Unix Commands - Search Man Pages

null(4) [opendarwin man page]

NULL(4) 						   BSD Kernel Interfaces Manual 						   NULL(4)

NAME
null -- the null device DESCRIPTION
The null device accepts and reads data as any ordinary (and willing) file - but throws it away. The length of the null device is always zero. FILES
/dev/null HISTORY
A null device appeared in Version 7 AT&T UNIX. BSD
June 5, 1993 BSD

Check Out this Related Man Page

PTY(4)							   BSD Kernel Interfaces Manual 						    PTY(4)

NAME
pty -- BSD-style compatibility pseudo-terminal driver SYNOPSIS
device pty DESCRIPTION
The pty driver provides support for the traditional BSD naming scheme that was used for accessing pseudo-terminals. When the device /dev/ptyXX is being opened, a new terminal shall be created with the pts(4) driver. A device node for this terminal shall be created, which has the name /dev/ttyXX. New code should not try to allocate pseudo-terminals using this interface. It is only provided for compatibility with older C libraries that tried to open such devices when posix_openpt(2) was being called. FILES
The BSD-style compatibility pseudo-terminal driver uses the following device names: /dev/pty[l-sL-S][0-9a-v] Pseudo-terminal master devices. /dev/tty[l-sL-S][0-9a-v] Pseudo-terminal slave devices. DIAGNOSTICS
None. SEE ALSO
posix_openpt(2), pts(4), tty(4) HISTORY
A pseudo-terminal driver appeared in 4.2BSD. BUGS
Unlike previous implementations, the master slave device nodes are destroyed when the PTY becomes unused. A call to stat(2) on a nonexistent master device will already cause a new master device node to be created. The master device can only be destroyed by opening and closing it. The pty driver cannot be unloaded, because it cannot determine if it is being used. BSD
August 20, 2008 BSD
Man Page

14 More Discussions You Might Find Interesting

1. UNIX for Dummies Questions & Answers

find & grep

Hi, I would like to know which files contain a certain string. If I use 'grep "string" *' only the working directory is being searched. I also want to search the subdirectories. When I use 'find . -type f -print |xargs grep "string" > dev/null' I get the message 'xargs: missing quote?'. What's... (11 Replies)
Discussion started by: Anika
11 Replies

2. UNIX for Dummies Questions & Answers

mv files to /dev/null

im having trouble with moving files in a directory into /dev/null for file in $HOME/.trashcan/ do mv $file /dev/null done the error msg i get is: mv: /dev/null: not a directory. does anyone know how to fix this? thanks primal (16 Replies)
Discussion started by: primal
16 Replies

3. Solaris

What is /dev/tty /dev/null and /dev/console

Hi, Anyone can help My solaris 8 system has the following /dev/null , /dev/tty and /dev/console All permission are lrwxrwxrwx Can this be change to a non-world write ?? any impact ?? (12 Replies)
Discussion started by: civic2005
12 Replies

4. Shell Programming and Scripting

comparing the null values in the unix

hi all, iam new to this forum.i have to submit the script EOD.so please help me. my requirement is to compare two null values..iam trying to compare two null values :One null value output of the storedprocedure and another iam giving spaces in script. it is giving the error... (11 Replies)
Discussion started by: bbc17484
11 Replies

5. IP Networking

gethostbyname_r returns NULL when hostname has dash

We have a code to find the DNS entry of a host that has a trailing '-' in its url (format example: mysite-.watch.com): if(gethostbyname_r(host,host_ent,host_buffer,host_buffer_size,&host_error)==NULL) { //failed } But when remove the '-' from the host name the code does not return... (12 Replies)
Discussion started by: uunniixx
12 Replies

6. UNIX for Dummies Questions & Answers

Check for null values in a column

Hi All, I have a file with 10 columns and get the required data for nine columns properly except 8th. In 8th column i have both NULL and NON NULL values...i.e certain records have values for all the columns including 8th column and certain records have 8th column as NULL.My requisite is,without... (20 Replies)
Discussion started by: ganesh_248
20 Replies

7. UNIX for Dummies Questions & Answers

data is seen as NULL after loading into database

hello, when I load a data from text file all the values become NULL in the table. Please help me with this problem. Thanks sheen (15 Replies)
Discussion started by: sheen
15 Replies

8. Shell Programming and Scripting

Newbie question: if[command not null]

hi, i have to put in my script a command that should tell me if the contents of two different paths are the same. I thought to write an "if" command who makes the diff of two files which contains the `ls` of the folders and go on with the script if is not null, but i'm afraid of the fact... (13 Replies)
Discussion started by: zangarules
13 Replies

9. Solaris

/dev/null not writable

Hi, after a server (solaris 10) got rebooted, Im faced with the problem that in one of my zones (whole zone) /dev/null is only writeable for root crw-r--r-- 1 root sys 13, 2 Jul 8 10:16 /dev/null Unfortunatly chmod didnt help at this point and since its a productive system I dont... (11 Replies)
Discussion started by: bin-doph
11 Replies

10. Shell Programming and Scripting

Averaging each row with null values

Hi all, I want to compute for the average of a file with null values (NaN) for each row. any help on how to do it. the sample file looks like this. 1.4 1.2 1.5 NaN 1.6 1.3 1.1 NaN 1.3 NaN 2.4 1.3 1.5 NaN 1.5 NaN 1.2 NaN 1.4 NaN I need to do a row-wise averaging such that it will sum only... (14 Replies)
Discussion started by: ida1215
14 Replies

11. Shell Programming and Scripting

Check null value in xml

Hi, I have a log file which is having some xml tags. I need to check the value for a particular xml field is null or not and if it is null i have to add current time as the value for that xml field. I tried below code to check whether the word count is 0. But even if the xml field is null it... (16 Replies)
Discussion started by: Neethu
16 Replies

12. Shell Programming and Scripting

Replace a field where values are null in a file.

Hi, I've a pipe delimited file and wanted to replace the 3rd field to 099990 where the values are null. How can I achieve it using awk or sed. 20130516|00000061|02210|111554|03710|2|205069|SM APPL $80-100 RTL|S 20130516|00000061|02210|111554|03710|2|205069|SM APPL $80-100 RTL|S... (12 Replies)
Discussion started by: rudoraj
12 Replies

13. Shell Programming and Scripting

awk print columns which are not null

I am working on a file with several columns as below MO_NAME,FAULT_TYPE,CLASS,CODE1,CODE2,CODE3 RXOCF-101,BTS INTERNAL,FAULT CODES CLASS 2A,53,58 RXOCF-101,BTS INTERNAL,FAULT CODES CLASS 2B,24 RXOCF-101,BTS INTERNAL,FAULT CODES CLASS 2A,33 RXOCF-101,BTS INTERNAL,FAULT CODES CLASS 2D,57 ... (12 Replies)
Discussion started by: Rizwan Rasul
12 Replies

14. Shell Programming and Scripting

To find record having null value

Hi All My requirement is to find the null values in particular column of a file and reject it in case if it contains null values. But the challenge is that I want a common command which can be used across different file, as the position of the column we need to check for different file may get... (14 Replies)
Discussion started by: ginrkf
14 Replies