Shell Programming and Scripting

I have a file contains thousands of lines. I want to insert n random numbers into each line at
specific position. Like this:

Code:

0      22……
1      33……
……
……

I want to insert 3 random numbers from position 2 to 4 into each line.

Code:

0  325  22……
1  685  33……
……
……

Moderator's Comments:

Please use CODE tags when displaying sample input, output, and code segments.

I don't understand your requirements.

How does changing two spaces that occupy the 4th and 5th characters on an input line into 3 digits meet the requirement to "insert 3 random numbers from position 2 to 4 into each line"?

As Don said, your example does not match the specification you gave. Maybe you didn't mean "insert 3 random numbers", but "replace the spaces (at a certain position) by a 3-digit random number"?

---------- Post updated at 08:18 AM ---------- Previous update was at 08:09 AM ----------

You did not say, what shell you want to use. I give you an example solution in Zsh (which is pretty convenient when it comes to programming):

Say you process your file line by line, and have stored one line in variable

Code:

line

, i.e. line contains somthing like

Code:

4     44

(i.e. 5 spaces between the numbers), and you want to replace the middle three spaces by a random number. This could be done in Zsh by

Code:

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

Note that there are 4 spaces between the pair of slashes, and exactly one space after the second slash. Hence, the expression substitutes the first four spaces in the line, by a single space followed by a 3-digit random number.

Except, of course, that you'll get a 1-digit random number about 10 times out of a thousand (replacing 4 spaces with 2 characters) and a 2-digit random number about 90 times out of a thousand (replacing 4 spaces with 3 characters).

my fault,sorry! offset 2 to 4 was reserved by fill with spaces at first. now, i want to use this position by replace spaces with
some random numbers for testing! thank you very much!

Changing the 4th and 5th characters on your input lines to 3-digit pseudo-random numbers in the output (as shown in your sample input and output) could be done with something like:

Code:

awk '
BEGIN {	srand()
}
{	printf("%s%03d%s\n", substr($0, 1, 3), rand() * 1000, substr($0, 6))
}' file

If you want to try this on a Solaris/SunOS system, change awk to /usr/xpg4/bin/awk or nawk.

You can adjust the number and positions of the characters replaced in your input lines to match the description of your requirements instead of matching the sample input and output you provided if you want to.

Ooops. You are right (and that's trivial to fix). Unless we are happy with leading zeroes in the random number, we should use

Code:

$((100+RANDOM%900))

instead.....