My input file has positions in first column with different number of spaces (or no space)
16504 16516
1650811 16520
1651 16524
16516111 16528
165204 16532
I need to get an output file where fist column has no spaces at all, while keeping second column as it is.
16504 16516
16508 16520
16512 16524
16516 16528
16520 16532
If this is just an alignment issue, and you want to line up the data into columns:
$ column -t somefile
16504 16516
1650811 16520
1651 16524
16516111 16528
165204 16532
The -t switch to column will create a table from the source data, automatically:
-t, --table
Determine the number of columns the input contains and create a
table. Columns are delimited with whitespace, by default,
or with the characters supplied using the separator. Table output
is useful for pretty-printing.
expand is another useful tool. I use expand when I post examples of output that include tabs. It removes them, substituting in spaces in their place. You can control the number of spaces w/ it.
You are likely after something like:
sed "s/^ *//" < your_file
which removes any leading spaces (replaces them with an empty string). If you also have variable number of spaces between the columns, you can extend it to:
sed "s/^ *//;s/ */ /g" < your_file
which (after removing the leading spaces) replaces any occurrence of one or more spaces with a fixed string (in this case 4 spaces). You may also want to use \s instead of plain space in the matching pattern to cover cases where a Tab character is used.
You can try this:
awk '$1=$1' file
to remove all leading space in first column.
column -t < input_file