Login or Register to Ask a Question and Join Our Community


UNIX for Dummies Questions & Answers

Understanding 2>&1

 
Thread Tools Search this Thread
Top Forums UNIX for Dummies Questions & Answers Understanding 2>&1
# 1  
Old 03-04-2009
Understanding 2>&1
Hi,

I have this line in a script:

if mt -f /dev/nst0 rewind > /tmp/status_nst0.log 2>&1 ; then [more code]


What does the 2>&1 mean? I think the line is saying that after rewinding the device if the log file does not exist then execute the code but I do not understand the contribution of the 2>&1.

Thanks!
# 2  
Old 03-04-2009
Hammer & Screwdriver
It will redirect Std-Error to Std-Output

In other words, it will send any error messages to whatever you have currently defined for output. Normal output would be your screen, but you can set this so output is going to a file.

Code:
ls -l >file1

will send your file listing to file1, error mesages will come to the screen

Code:
ls -l 2>&1 >file2

will send the file listing and errors to file2
# 3  
Old 03-04-2009
1 is std output
2 is std error

2 >&1 means redirect std error to std output wihich is /tmp/status_nst0.log in the exemple you posted. Its in no way in relation with your device.
 
Login or Register to Ask a Question

Previous Thread | Next Thread

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

SFTP Shell Script Get & Delete && Upload & Delete

Hi All, Do you have any sample script, - auto get file from SFTP remote server and delete file in remove server after downloaded. - only download specify filename - auto upload file from local to SFTP remote server and delete local folder file after uploaded - only upload specify filename ... (3 Replies)
Discussion started by: weesiong
3 Replies

2. Solaris

Understanding & Monitoring CPU performance (Load vs SAR)

Hi all, Been reading a lot of the cpu load and its "analogy of it to car traffic path of expressway" From wiki Most UNIX systems count only processes in the running (on CPU) or runnable (waiting for CPU) states. However, Linux also includes processes in uninterruptible sleep states... (13 Replies)
Discussion started by: javanoob
13 Replies

3. Shell Programming and Scripting

help understanding regex with grep & sed

I have the following line of code that works wonders. I just don't completely understand it as I am just starting to learn regex. Can you help me understand exactly what is happening here? find . -type f | grep -v '^\.$' | sed 's!\.\/!!' (4 Replies)
Discussion started by: trogdortheburni
4 Replies

4. Shell Programming and Scripting

Replace & sign to &amp word

Hi, I have text file abc.txt. In this file, I have the following data. Input: Mr Smith &amp Mrs Smith Mr Smith &apos Mrs Smith Mr Smith & Mrs Smith Mr Smith& Mrs Smith Mr Smith &Mrs Smith Output: Mr Smith &amp Mrs Smith Mr Smith &apos Mrs Smith Mr Smith &amp Mrs Smith Mr Smith&amp... (4 Replies)
Discussion started by: naveed
4 Replies

5. Shell Programming and Scripting

replace & with & xml file

Hello All I have a xml file with many sets of records like this <mytag>mydata</mytag> <tag2>data&</tag2> also same file can be like this <mytag>mydata</mytag> <tag2>data&</tag2> <tag3>data2&amp;data3</tag3> Now i can grep & and replace with &amp; for whole file but it will replace all... (4 Replies)
Discussion started by: lokaish23
4 Replies

6. Shell Programming and Scripting

Understanding ampersand (&) usage in the command

Please explain the usage of ampersand in the following command who & echo "Total number of users are `who|wc -l`" What I understand is that ampersand is used to run some process in the background. And, what I am expecting from this command is "Output of who should be displayed on the... (2 Replies)
Discussion started by: Shan_u2005
2 Replies

7. Shell Programming and Scripting

PHP read large string & split in multidimensional arrays & assign fieldnames & write into MYSQL

Hi, I hope the title does not scare people to look into this thread but it describes roughly what I'm trying to do. I need a solution in PHP. I'm a programming beginner, so it might be that the approach to solve this, might be easier to solve with an other approach of someone else, so if you... (0 Replies)
Discussion started by: lowmaster
0 Replies

8. Shell Programming and Scripting

Find & Replace string in multiple files & folders using perl

find . -type f -name "*.sql" -print|xargs perl -i -pe 's/pattern/replaced/g' this is simple logic to find and replace in multiple files & folders Hope this helps. Thanks Zaheer (0 Replies)
Discussion started by: Zaheer.mic
0 Replies

9. UNIX for Dummies Questions & Answers

Problem with xterm & tcsh & sourcing a script in a single command

Hi friends, I have a script that sets the env variable path based on different conditions. Now the new path variable setting should not done in the same terminal or same shell. Only a new terminal or new shell should have the new path env variable set. I am able to do this only as follows: >cd... (1 Reply)
Discussion started by: sowmya005
1 Replies

10. UNIX for Dummies Questions & Answers

Search for & edit rows & columns in data file and pipe

Dear unix gurus, I have a data file with header information about a subject and also 3 columns of n rows of data on various items he owns. The data file looks something like this: adam peter blah blah blah blah blah blah car 01 30 200 02 31 400 03 57 121 .. .. .. .. .. .. n y... (8 Replies)
Discussion started by: tintin72
8 Replies
Login or Register to Ask a Question