NULL(4) BSD Kernel Interfaces Manual NULL(4)NAME
null -- the null device
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.
A null device appeared in Version 7 AT&T UNIX.
BSD June 5, 1993 BSD
Check Out this Related Man Page
TTYNAME(3) BSD Library Functions Manual TTYNAME(3)NAME
isatty, ttyname, ttyslot -- get name of associated terminal (tty) from file descriptor
Standard C Library (libc, -lc)
These functions operate on the system file descriptors for terminal type devices. These descriptors are not related to the standard I/O FILE
typedef, but refer to the special device files found in /dev and named /dev/ttyxx and for which an entry exists in the initialization file
/etc/ttys. (See ttys(5).)
The isatty() function determines if the file descriptor fildes refers to a valid terminal type device.
The ttyname() function gets the related device name of a file descriptor for which isatty() is true.
The ttyslot() function fetches the current process' control terminal number from the ttys(5) file entry.
The ttyname() function returns the null terminated name if the device is found and isatty() is true; otherwise, a NULL pointer is returned.
The ttyslot() function returns the unit number of the device file if found; otherwise, the value zero is returned.
SEE ALSO ioctl(2), ttys(5)HISTORY
A isatty(), ttyname(), and ttyslot() function appeared in Version 7 AT&T UNIX.
The ttyname() function leaves its result in an internal static object and returns a pointer to that object. Subsequent calls to ttyname()
will modify the same object.
BSD June 4, 1993 BSD
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)
im having trouble with moving files in a directory into /dev/null
for file in $HOME/.trashcan/
mv $file /dev/null
the error msg i get is:
mv: /dev/null: not a directory.
does anyone know how to fix this?
primal (16 Replies)
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)
We have a code to find the DNS entry of a host that has a trailing '-' in its url (format example: mysite-.watch.com):
But when remove the '-' from the host name the code does not return... (12 Replies)
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)
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)
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)
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)
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)
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)
I am working on a file with several columns as below
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)
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)