How to remove leading whitespace from each line?

**Conraad** · 22-02-2010

Hello friends,
I have one problem in my file. I have one file which look like following:

Code:

for (a = 0; a < 100; a++)
    for (a = 0; a < 100; a++)
  for (a = 0; a < 100; a++)
       for (a = 0; a < 100; a++)
     for (a = 0; a < 100; a++)
           for (a = 0; a < 100; a++)
for (a = 0; a < 100; a++)

I want to convert above file into following:

Code:

for (a = 0; a < 100; a++)
for (a = 0; a < 100; a++)
for (a = 0; a < 100; a++)
for (a = 0; a < 100; a++)
for (a = 0; a < 100; a++)
for (a = 0; a < 100; a++)
for (a = 0; a < 100; a++)

How can this be done? Can anyone tell me how to remove leading whitespace from each line? Please help me.

**Reegan** · 22-02-2010

Hey it very simple to remove leading whitespace from each line. You have to just use one simple command in your unix editor to do this. You have to use sed command to do this. Just type following command into your unix and press enter.

Code:

sed "s/^[ \t]*//" -i filename

**opaper** · 22-02-2010

As per my information you have to use sed command to do this. It is very easy to use and implement. I have written following command for you. Just try to understand this.

Code:

$ sed 's/^ *//gs' < inputs.txt > outputs.txt

Above command take two file one input file and output file. From input file we take original data and in output file we store modified data.

**MindSpace** · 22-02-2010

It is very easy process to remove leading whitespace from each line. You have to just use following command in your unix editor to fix this problem.

Code:

$ sed 's/^[ \t]+//g' < input.txt > output.txt

In above code "s" means "substitute". The /'s are the delimiters for the patterns. The value between the first two /'s are used to match pattern and data between the 2nd and 3rd / is the data to replace it with.

**Modifier** · 22-02-2010

Hey there are two methods to do this. The first one is awk command. Using this you will get following output.
you can use awk

Code:

$ awk '{$1=$1}1' file
for (a = 0; a < 100; a++)
for (a = 0; a < 100; a++)
for (a = 0; a < 100; a++)
for (a = 0; a < 100; a++)
for (a = 0; a < 100; a++)
for (a = 0; a < 100; a++)
for (a = 0; a < 100; a++)

The second one is sed command. You will get following output using this command.

Code:

$ sed 's|^[[:blank:]]*||gs' file
for (a = 0; a < 100; a++)
for (a = 0; a < 100; a++)
for (a = 0; a < 100; a++)
for (a = 0; a < 100; a++)
for (a = 0; a < 100; a++)
for (a = 0; a < 100; a++)
for (a = 0; a < 100; a++)

**ranjankumar09** · 23-02-2010

Do you want to preserve "empty" lines or delete them ?

Here is an alternate biterscripting script with line-by-line control.

Code:


# Script LeadingWhiteSpaces.txt
var str file, content, line, output
cat $file > $content ; lex "1" $content > $line
# Go line by line.
while ($line <> "")
do
    # Extract the line starting at the first printable char.
    stex -r -c "[^.^" $line >> $output
    lex "1" $content > $line
done
echo $output > { echo $file }

Run script as

Code:

script "LeadingWhiteSpaces.txt" file("C:/somefolder/somefile.cpp")

Will clean the file C:/somefolder/somefile.cpp of beginning white spaces ... assuming you saved the script in some folder in your $path as "LeadingWhiteSpaces.txt".