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Adding a line if not present

Posted on 2003-12-02
5
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Last Modified: 2010-04-22
Dear experts.

Please tell me how to make a bash function to add a line if that line is not present in a file.

The file is /etc/ld.so.conf, it is like this
=========
/usr/lib
/usr/X11R6/lib
=========

Here is my script that does not work.
-------------------
function add_ldconfig()
{
    cat /etc/ld.so.conf | while read line; do
        if [ "$1" = "$line" ]; then
            return 0
        fi
    done
    echo $1 >> /etc/ld.so.conf
}
--------------------

if the function is called like this
add_ldconfig /opt/kde/lib

it should modify the file into
=========
/usr/lib
/usr/X11R6/lib
/opt/kde/lib
=========

But
add_ldconfig /usr/X11/lib

would not change anything.

So far, my script always add the entry.
0
Comment
Question by:Kocil
[X]
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5 Comments
 
LVL 45

Expert Comment

by:sunnycoder
ID: 9864559
grep "line_to_add" file_to_add_to
if [ $? -eq 1 ]
then
       echo "line_to_add" >> file_to_add_to
fi
0
 
LVL 5

Author Comment

by:Kocil
ID: 9865122
Thanks sunny, but your script failed when the file_to_add_to was
==========
/usr/local/lib
/usr/X11R6/lib
/usr/lib/qt/lib
==========

and the line_to_add = /usr/lib.

I found options -x works though.

by the way ... I wonder why in my script,
'return' does not quit immediatelly from the function ?
It only quits from the while block. Same as 'break'.

A modified like this below was also not working.

   present=0
   cat /etc/ld.so.conf | while read line; do
       if [ "$1" = "$line" ]; then
           present=1
           echo $present
           break
       fi
   done
   echo $present
   if [ present = 0 ]; then
       echo $1 >> /etc/ld.so.conf
   fi

The present inside the loop was changed to 1, but outside the loop, it backs to 0.
Strange.
My bash is version 2.05b.0


Thanks.

0
 
LVL 45

Accepted Solution

by:
sunnycoder earned 800 total points
ID: 9873270
>The present inside the loop was changed to 1, but outside the loop, it backs to 0.
http:/Q_20681247.html

script that I posted in my last post works perfectly fine at my system ... bash 2.05.8
what was the error encountered at your end ?
check carefully for spaces
0
 
LVL 5

Author Comment

by:Kocil
ID: 9875829
> what was the error encountered at your end ?

grep /usr/lib file_to_add_to

would match any line with /usr/lib, including /usr/lib/qt/lib
So it' won't attach it.

However
grep -x /usr/lib file_to_add_to

works perfectly.

Thanks for the last link for the pipe problem. All clear now.
You are great.
0
 
LVL 45

Expert Comment

by:sunnycoder
ID: 9880140
oh ... never thought of that scenario...
when you mentioned -x, I though -x for debugging :-D and thus could not make much sense out of the last post...

alls well that ends well :o)
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