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Cat Input & Output to a Log file


 
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# 1  
Cat Input & Output to a Log file

Team,

we use below command to store the contents in a logfile.

Code:
cat a.txt > a.log

a.txt content is

Code:
123
345

Is there any options available to store the command used also?

for eg a.log may show as

Code:
cat a.txt
123
345

# 2  
You can do it like this:
Code:
echo cat a.txt > a.log
cat a.txt >> a.log

# 3  
Code:
{ echo cat a.txt; cat a.txt; } >> a.log

# 4  
Hello,

Here is one more approach.

Code:
echo "cat a.txt" | cat - a.txt >> brnew.txt

Output will be for file as follows.

Code:
$ cat brnew.txt
cat a.txt
abc    def
def    xyz
123   5678


Thanks,
R. Singh
# 5  
When needing to see the command because troubleshooting a script you may want to use
Code:
set -x

in your script.
The following commands may also be of interest :
Code:
man tee

Code:
man exec

If you want to log your session into a file (what you type and what you get), also have a look at
Code:
man script

Little example below :
Code:
# script my.log
Le script a commencé, le fichier est my.log
# cat a.txt
123
345
# exit
Script terminé, le fichier est my.log
# cat my.log
Début du script sur mer 18 déc 2013 15:30:57 CET
# cat a.txt
123
345
# exit

Script terminé sur mer 18 déc 2013 15:31:07 CET
#

In blue the content of the my.log file
# 6  
Try this (but you won't see what you type);
Code:
exec 5>&1 6>&2 >&a.log
cat a.txt
exec  1>&5 2>&6

This saves stdout and stderr to some dummy file descriptors, redirects them to x.log, and later restores them from the dummies.
 

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