You need to understand the theory first and then its upto you how and where you want to apply that theory. I'll try to explain above to you.
The greater-than (>) in commands like these redirect the program's output somewhere. In this case, something is being redirected into /dev/null, and something is being redirected into &1.
Standard in, out and error:
There are three standard sources of input and output for a program. Standard input usually comes from the keyboard if it's an interactive program, or from another program if it's processing the other program's output. The program usually prints to standard output, and sometimes prints to standard error. These three file descriptors (you can think of them as “data pipes”) are often called STDIN, STDOUT, and STDERR.
Sometimes they're not named, they're numbered! The built-in numberings for them are 0, 1, and 2, in that order. By default, if you don't name or number one explicitly, you're talking about STDOUT.
That means file descriptor 0 or fd0 denotes STDIN or standard input and file descriptor 1 or fd1 denotes STDOUT or standard output and file descriptor 2 or fd2 denotes STDERR or standard error.
You can see the command above is redirecting standard output into /dev/null, which is a place you can dump anything you don't want (often called the bit-bucket), then redirecting standard error into standard output (you have to put an & in front of the destination when you do this).
The short explanation, therefore, is “all output from this command should be shoved into a black hole.” That's one good way to make a program be really quiet!
Regards,
Tayyab
These 6 Users Gave Thanks to tayyabq8 For This Post:
while (my $row = $sth->fetchrow_arrayref) {
$var->{"@$row"}=" ";
}
Can anyone help me understanding above mentioned.
i) As per my knowledge $row is taking ARRAY Refernce from the database
ii) @$row is containing the value of 0th index of the array, testted the same.
but I am not able... (0 Replies)
I need to sort the following file by the rhdiskpower devices in the last column:
Total_MB Free_MB OS_MB Name Failgroup Library Label UDID Product Redund Path
1024 851 1024 OCRVOT1_0000 OCRVOT1_0000 System UNKNOWN ... (3 Replies)
How are these two different? They both prevent output and error from being displayed. I don't see the use of the "&"
echo "hello" > /dev/null 2>&1
echo "hello" > /dev/null 2>1 (3 Replies)
I am new to unix and learning. Came across this statement
cmd 2>/dev/null/ <<EOF
2>/dev/null/ denotes that std error is stored in /dev/null but that is considered as a non-existent file!! What does << EOF mean and how does it affect?
I am really confused.. :wall:
Can some one explain this... (2 Replies)
why is this giving me errors?
i type this in: find / -name "something.txt" 2>/dev/null
i get the following error messages:
find: bad option 2
find: path-list predicate-list
:confused: (5 Replies)
Hi Guys,
I'm sorry but I can't find answer for this, what is the meaning of -s option in "if" statement on unix scipting. Please see sample below:
opath=/home/output
for i in N1 N2 N3 N4
do
echo $i
if
then
grep $i $opath/N5_CRAI > $opath/N5_$i.crai
chmod 777 $opath/N5_$i.crai
... (7 Replies)
I apologize if this question has been answered else where or is too elementary.
I ran across a KSH script (long unimportant story) that does this:
if ; then
CAS_SRC_LOG="/var/log/cas_src.log 2>&1"
else
CAS_SRC_LOG="/dev/null 2>&1"
fithen does this:
/usr/bin/echo "heartbeat:... (5 Replies)
Hi all.
I have a .txt file that I need to sort it
My file is like:
1- 88 chain0 MASTER (FF-TE) FFFF 1962510 /TCK T FD2TQHVTT1 /jtagc/jtag_instreg/updateinstr_reg_1 dff1 (TI,SO)
2- ... (10 Replies)