Meaning of 2>/dev/null/ <<EOF ?


 
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# 1  
Old 04-27-2011
Meaning of 2>/dev/null/ <<EOF ?

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.. Smilie
Can some one explain this staement.

Any help appreciated..
# 2  
Old 04-27-2011
/dev/null is a special character device file, and has nothing to do with the << EOF part of the code you post.

Code:
$ ls -l /dev/null
crw-rw-rw-    1 root     system        2,  2 Apr 27 13:45 /dev/null

<< EOF is the open of a here-document:

Quote:
man ksh

<<[-]word The shell input is read up to a line that is the same as word
So, in your case:
Code:
cmd 2>/dev/null/ <<EOF
feed cmd here
....
....
EOF

This User Gave Thanks to Scott For This Post:
# 3  
Old 04-27-2011
Code:
/dev/null

is a sink; think of it as a "black hole", where you can dump what you don't want.
By doing 2> /dev/null, you are dumping the stderr.
Code:
$ ls -l nonexistentFile
ls: nonexistentFile: No such file or directory

Code:
$ ls -l nonexistentFile 2>/dev/null

The error message is sent to the sink.

The here-document (<<EOF construct) is used to create a name-less file.
Code:
cmd <<EOF
line1
line2
EOF

is the same as
Code:
cmd file

where file contains:
Code:
line1
line2

This User Gave Thanks to mirni For This Post:
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