Output command

Thread Tools Search this Thread
Top Forums Shell Programming and Scripting Output command
# 1  
Old 11-28-2002
Output command


when i execute the following command

$sort list
i get the list sorted out onto my screen

if i use
$sort list >listsort
i get an file listsort with the list sorted out

If i use
$sort list >list
i get an empty file list

also when i use
$sort list | >list
i get an empty file

Can somebody tell me how to put the sorterd list immediatly in the same file 'list' ?

Thanks alot four your response !!

A ducatiloving scriptnewbie
# 2  
Old 11-28-2002
If this is something that you will be doing a lot of in a script or something similiar, wrap the sort command in a shell script that sorts the list to a temp file and mv the temp file to the original filename.
# 3  
Old 11-29-2002
This is a dangerous thing to do berty007. If things go wrong you will not have the source file anymore and thus repairing the damage would be a hassel (you would have to rebuild the source file!)

you could do a test to ensure the new file contains data (test -s <filename> ) before deleteing the original.
# 4  
Old 11-29-2002
You absolutely need an input file and an output file. You can't get around that. You can remove the name from the input file and re-use it for the output file. Like this:
(exec < list ; rm list ; sort > list)

but like Ralf says, this is dangerous.
# 5  
Old 11-29-2002
The reason that "$ sort list >list" leaves you with an empty file is that the shell sees that you want output to go to "list" (with >list). Before it even begins that command, it ither creates or truncates the output file. Now you just sorted the file you truncated.
Login or Register to Ask a Question

Previous Thread | Next Thread

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

Insert title as output of command to appended file if no output from command

I am using UNIX to create a script on our system. I have setup my commands to append their output to an outage file. However, some of the commands return no output and so I would like something to take their place. What I need The following command is placed at the prompt: TICLI... (4 Replies)
Discussion started by: jbrass
4 Replies

2. UNIX for Dummies Questions & Answers

Set Command to output a log of every command executed in the script

Hi Guys, I like to output every command executed in the script to a file. I have tried set -x which does the same. But it is not giving the logs of the child script which is being called from my script. Is there any parameters in the Set command or someother way where i can see the log... (2 Replies)
Discussion started by: mac4rfree
2 Replies

3. Red Hat

Command understanding the output file destination in case of standard output!!!!!

I ran the following command. cat abc.c > abc.c I got message the following message from command cat: cat: abc.c : input file is same as the output file How the command came to know of the destination file name as the command is sending output to standard file. (3 Replies)
Discussion started by: ravisingh
3 Replies

4. Shell Programming and Scripting

Want to terminate command execution when string found in the command output

Hi Experts, I am very much new to linux scripting, I am currently working on reducing my manual work and hence writing a script to automate few task. I am running below command to snmpwalk the router.. snmpwalk -v 3 -u WANDL_SU -a MD5 -A vfipmpls -x DES -X VfIpMpLs -l authPriv... (19 Replies)
Discussion started by: Hanumant.madane
19 Replies

5. UNIX for Dummies Questions & Answers

passing command output from one command to the next command in cshell

HI Guys, I hope you are well. I am trying to write a script that gets executed every time i open a shell (cshell). I have two questions about that 1) I need to enter these commands $ echo $DISPLAY $ setenv $DISPLAY output_of_echo_$display_command How can i write a... (2 Replies)
Discussion started by: kaaliakahn
2 Replies

6. AIX

Non interactive command output using script command ?

Hello, Script command helps to save command output to file. (Redicection doesn't work in this case). Besides interactive shell 'recording', Linux script command has "-c" option which allows to record output of some non-interactive command. The problem is that AIX script command variant... (6 Replies)
Discussion started by: vilius
6 Replies

7. UNIX for Dummies Questions & Answers

read command - using output from command substitution

Hey, guys! Trying to research this is such a pain since the read command itself is a common word. Try searching "unix OR linux read command examples" or using the command substitution keyword. :eek: So, I wanted to use a command statement similar to the following. This is kinda taken... (2 Replies)
Discussion started by: ProGrammar
2 Replies

8. UNIX for Advanced & Expert Users

Repeat output of last command w/o repeating last command

Is there a way to repeat the output of the last command for filtering without running the command again? All I could think of was to copy all the data to a text file and process it that way, is there another way? Like say I want to grep server.server.lan from a dtrace that was pages long after I... (5 Replies)
Discussion started by: glev2005
5 Replies

9. UNIX for Dummies Questions & Answers

Command display output on console and simultaneously save the command and its output

Hi folks, Please advise which command/command line shall I run; 1) to display the command and its output on console 2) simultaneous to save the command and its output on a file I tried tee command as follows; $ ps aux | grep mysql | tee /path/to/output.txt It displayed the... (7 Replies)
Discussion started by: satimis
7 Replies

10. UNIX for Dummies Questions & Answers

problem with output of find command being input to basename command...

Hi, I am triying to make sure that there exists only one file with the pattern abc* in path /path/. This directory is having many huge files. If there is only one file then I have to take its complete name only to use furter in my script. I am planning to do like this: if ; then... (2 Replies)
Discussion started by: new_learner
2 Replies
Login or Register to Ask a Question