Shell Script Commands

shandy^^^ · 02-09-2006, 03:19 AM

Hello!

Is there a command that would search for a text in a file and will return a certain value?

Thanks...

satinet · 02-09-2006, 03:49 AM

grep

it returns what you search for. like all commands it also returns exit values that can be called from $?

kshkid · 02-09-2006, 04:02 AM

these are the return values for grep,

0 - match found ( could be one or more )
1- no match
2- other errors ( no such file )

i have encountered only the above three return values

satinet · 02-09-2006, 04:35 AM

yep.

in a shell script you can call the last return value (from the last command) using $? e.g

awk '{ print $1}' /etc/passwd |grep someuser > /dev/null 2>&1

if test $? = 1
then
echo "this user does not exist"
fi

obviously that's a trite example, but it is useful.

shandy^^^ · 02-09-2006, 07:49 AM

Thank You satinet and kshkid!

In this line below:

awk '{ print $1}' /etc/passwd |grep someuser > /dev/null 2>&1

the file that im going to search is a log file which is /var/log/messages
But when I try it... It can't find any of words inside the log file eventhough it's in the log file. Why is that so?

kshkid · 02-09-2006, 07:58 AM

if u need to search with awk then,

Code:

awk ' /<searchword>/ {print}' /var/log/messages

shandy^^^ · 02-09-2006, 08:16 AM

kshkid,

it would return this message...

awk: cmd. line:1: fatal: cannot open file `/var/og/messages' for reading (No such file or directory)

kshkid · 02-09-2006, 08:23 AM

Quote:

Originally Posted by shandy^^^

kshkid,

it would return this message...

awk: cmd. line:1: fatal: cannot open file `/var/og/messages' for reading (No such file or directory)

Is the /var/log/messages file available?

I could find a typo in the file name /var/og/messages

can you please post the command line entry that you had tried?

shandy^^^ · 02-09-2006, 08:37 AM

Yes, the /var/log/messages is the log file of the Fedora Core4.

This is the script, filename: file5

Code:

#!/bin/sh
awk '/<tezt>/ {print}' /var/log/messages

if test $? = 1
then
echo "this user does not exist"
else
echo "this exist"
fi

chmod 777 file5

./file5

and it would return "this exist" eventhoung the word i search "tezt" can not be found in the log file.

kshkid · 02-09-2006, 08:51 AM

Quote:

Originally Posted by shandy^^^

Yes, the /var/log/messages is the log file of the Fedora Core4.

This is the script, filename: file5

Code:

#!/bin/sh
awk '/<tezt>/ {print}' /var/log/messages

if test $? = 1
then
echo "this user does not exist"
else
echo "this exist"
fi

chmod 777 file5

./file5

and it would return "this exist" eventhoung the word i search "tezt" can not be found in the log file.

no shandy, this is not what i meant, sorry for the communication gap.

Code:

if [ `awk ' /tezt/ {print}' /var/log/messages | wc -l` -eq 0 ]
then
echo "no such user"
else
echo "user exists"
fi

shandy^^^ · 02-09-2006, 09:15 AM

aaahhh yah its working already thanks...

do you know how to write a string into an existing text file?

kshkid · 02-09-2006, 09:25 AM

i cannot get your question,

do you mean replacing text,

or appending ?

can you please explain elaborately?

shandy^^^ · 02-09-2006, 09:38 AM

i have two files: file1 and file2
i want the files of file1 to be copied to file2... as in it would overwrite the existing files in the file2

did you get?

when I use 'cat file1 >> file2'
and when i execute over and again the command it would just concantenate the files of file1 to file2 but not overwrite...

shandy^^^ · 02-09-2006, 09:40 AM

i have two files: file1 and file2
i want the files of file1 to be copied to file2... as in it would overwrite the existing files in the file2

did you get?

when I use 'cat file1 >> file2'
and when i execute over and again the command it would just concantenate the files of file1 to file2 but not overwrite...

kshkid · 02-09-2006, 09:53 AM

to append file1 contents to file2

cat file1 >> file2

to overwrite file2 contents with file1

cat file1 > file2
or
mv file1 file2
or
cp file1 file2