How do I discard the last n characters of a string.

For example,

x=abcd1234.xyz

I want

y=abcd1234

What do I need to apply on x to get y?

Also related, I want to discard the characters before 1234

so y would have

y=1234

after the manipulation.

I know I can use perl substring but I am trying to do this in shell.

Also x may be 'abcdef1234.myfile' , hence care should be taken to discard a variable number of characters both back or front without specifying the position of beginning of the substring '1234'.

thanks in advance.

Hi,
try this :
If your string x contain a pipe then you have to change the FS variable and the line "z=$x......." to another character which surely not contains in x.

for example :

z=$x"@"$a"@"$b
y=`echo $z | awk ' BEGIN { FS="@"}


Hope, I can help you out by your problem !


x="abcdef1234.myfile"
echo "How many charakters do you want to discard in the front ?"
read a
echo "How many charakters do you want to discard at the end ?"
read b
z=$x"|"$a"|"$b
y=`echo $z | awk ' BEGIN { FS="|"}
{
y=substr($1,$2+1)
len=length(y)
y=substr(y,1,len-$3)
print y
}'`
echo "old_string "$x
echo "new_string "$y

Yes, it worked! THANKS A LOT!!!

-Jay in San Francisco, Sunny California.

You can try this.

x=abcd1234.xyz

To get rid off .xyz from x
y=${x%%.*}
echo $y (Should give out abcd1234)

To get rid off 1234 from y
z=${y%%1234*}
echo $z (Should see abcd)

Another method

x=abc1234.xyz
p=3
s=4

echo "$x" | sed -e 's/.\{3\}\(.*\).\{4\}$/\1/' => 1234

echo "$x" | sed -e 's/.\{'$p'\}\(.*\).\{'$s'\}$/\1/' => 1234

Thank you all. I definitely have learned something from everyone here.

AS Ram, Your solution is very elegant!

-jay,

Sorry Mr.cjaykumar,
that was your question !

//Also x may be 'abcdef1234.myfile' , hence care should be taken to discard a variable number of characters both back or front without specifying the position of beginning of the substring '1234'.//

I dont know how you can specify any variable number of characters both back or front in the solution from asram.