How to delete the first column ( which is in fact row names) from a data file in linux?

Question

I have data file with many thousands columns and rows. I want to delete the first column which is in fact the row counter. I used this command in linux:

cut          


        

Answer 1

As @karakfa notes, it looks like it's the leading whitespace which is causing your issues.

Here's a sed oneliner to do the job (that will account for spaces or tabs):

sed -i.bak "s|^[ \t]\+[0-9]\+[ \t]\+||" input.txt

Explanation:

-i       edit existing file in place
.bak     backup original file and add .bak file extension (can use whatever you like)

s        substitute
|        separator (easiest character to read as sed separator IMO)
^        start match at start of the line
[ \t]    match space or tab
\+       match one or more times (escape required so sed does not interpret '+' literally)
[0-9]    match any number 0 - 9

As noted; the input.txt file will be edited in place. The original content of input.txt will be saved as input.txt.bak. Use just -i instead if you don't want a backup of the original file.

Also, if you know that they are definitely leading spaces (not tabs), you could shorten it to this:

sed -i.bak "s|^ \+[0-9]\+[ \t]\+||" input.txt