Remove first character of a string in Bash

I need to calculate md5sum of one string (pathfile) per line in my ls dump, directory_listing_file:

./r/g4/f1.JPG
./r/g4/f2.JPG
./r/g4/f3.JPG
./r/g4/f4.JPG

But that md5sum should be calculated without the initial dot. I've written a simple script:

while read line
do
    echo $line | exec 'md5sum'
done

./g.sh < directory_listnitg.txt

How do I remove the first dot from each line?

myString="${myString:1}"

Starting at character number 1 of myString (character 0 being the left-most character) return the remainder of the string. The "s allow for spaces in the string. For more information on that aspect look at $IFS.

You can pipe it to

cut -c2-

Which gives you

while read line
do
echo $line | cut -c2- | md5sum
done

./g.sh < directory_listnitg.txt

remove first n characters from a line or string

#method1) using bash

 str="price: 9832.3"
 echo "${str:7}"

#method2) using cut

 str="price: 9832.3"
 cut -c8- <<< $str

#method3) using sed

 str="price: 9832.3"
 cut -c8- <<< $str

#method4) using awk

 str="price: 9832.3"
 awk '{gsub(/^.{7}/,"");}1' <<< $str

Set the field separator to the path separator and read everything except the stuff before the first slash into $name:

while IFS=/ read junk name
do
    echo $name
done < directory_listing.txt

Different approach, using sed, which has the benefit that it can handle input that doesn't start with a dot. Also, you won't run into problems with echo appending a newline to the output, which will cause md5sum to report bogus result.

#!/bin/bash

while read line
do
     echo -n $line | sed 's/^.//' | md5sum
done < input

compare these:

$ echo "a" | md5sum
60b725f10c9c85c70d97880dfe8191b3  -

$ echo -n "a" | md5sum
0cc175b9c0f1b6a831c399e269772661  -

Remove first character of a string in Bash

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