Shell Programming and Scripting

Hi roof,
Why don't you think 000 and 029 just as valid as 3-digit random numbers as 100 and 999?

Assuming that characters two through four on every input line are spaces (which was not stated in the requirements, but is true in the given 2-line sample input) and you're using a recent bash, a 1993 or later ksh, or zsh, you could change your suggestion from:

Code:

echo ${line:s/    / $((RANDOM%1000))}

to:

Code:

echo ${line:s/    / $((RANDOM%10))$((RANDOM%10))$((RANDOM%10))}

to change characters three through five to a 3-digit random number in the given sample input.

But, hhdzhu still hasn't given us a clear specification of what output is desired. (Specifying offsets 2 to 4 are to be changed is ambiguous since we haven't been told whether the 1st character on a line is offset 0 (as in bash and recent ksh ${variable:offset[:length]}) or offset 1 (as in awk substr(string, offset[, length])) and sample input and output that does' t match either of these.

And, since the input is "thousands of lines", it isn't obvious whether or not my awk suggestion would be slower or faster processing the desired file than the zsh (or ksh93 or bash) script you suggested (modified as shown above) inserted into a while read loop to process the entire file instead of just one line.

I didn't say it isn't, but it might be. Some people consider a 3-digit number as one which is higher than 99 (and might be disappointed, if they get promised an hourly payment in the "range of a 3-digit-number" and end up getting payed US$ 002 per hour), and others are happy with a leading zero. The OP didn't say anything, and I gave my implementation as an example.

To be honest, even for a couple of thousands of lines, speed difference should only matter if the same type of transformation is done many times in a loop. I gave zsh as an example, because I personally use either zsh or Ruby for this type of task (out of a habit), but bash, Perl, Python, awk etc. work of course equally well, and the OP did not have expressed a preference for a particular language.