changing the first number of every line

Dear Monks,

I am relatively new to perl and would like to request for a code that would enable me to change the first number of a line of vectors for all lines in the txt file.

An example of the vectors looks like this:

0 1:120.000000 2:0.000000 3:120.000000 4:262.000000 5:120.000000 6:349.000000

Every line starts with 0, and i would like to replace that 0 with 1

I have around 100 of these lines in my file and any help would be greatly appreciated!

Comment on changing the first number of every line
Re: changing the first number of every line by choroba (Prior) on Nov 21, 2012 at 13:14 UTC
`perl -i~ -p -e 's/^0/1/' *.txt` [download] `-i` changes the files, backups are created with the `~` appended `-p` prints each line after applying the code. The code just replaces 0 at the beginning of a line with 1. لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ	[reply] [d/l] [select]
Re: changing the first number of every line by roboticus (Canon) on Nov 21, 2012 at 13:15 UTC
jinism: You can get a good start with that by reading perlintro and look over perlfaq5, especially the section "How do I change, delete, or insert a line in a file, or append to the beginning of a file?". ...roboticus When your only tool is a hammer, all problems look like your thumb.	[reply]
Re: changing the first number of every line by ww (Chancellor) on Nov 21, 2012 at 14:58 UTC
...and you can get a better start here if you'll read the docs; particularly, On asking for help and How do I post a question effectively?. Despite Parson choroba's generous response, this is NOT code-a-matic. We try to help those like yourself -- "new to perl" -- by helping them learn; not by solving their problems. So next time you have a problem like this; try to organize your thoughts about how you'd do the job on paper, and then, using `perldoc -f function` and the fine Tutorials here, try to come up with code to solve your quandry. If it works, you've really learned something; if it doesn't, and you can't figure out "why," then by all means, come back with the issue, your code (and data; each wrapped in <c>...</c> tags), an explanation of how your code fails to satisfy your intent, and verbatim quotes of any error messages or warnings. P.S. `use strict; use warnings;` or a recent enough version of Perl that invoking the version (for example, `use 5.014;`) does so for you. Those pragmas alone will help you find many sneaky little mistakes (to say nothing of big ones. PPS: If the solution choroba provided doesn't work for you, check that the quoting used is that required by your system -- windoze won't like what you've been given.	[reply] [d/l] [select]


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changing the first number of every line

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