1
1
I wrote C++ code and now I want to replace the number in a string by using shell scripts.
The part that needs to be replaced:
if (random<=90)
How I can change the 90 from a shell script?
I wrote this but I need something efficient other than sed or with a better regular expression just to match the number itself.
for i in {1..1000..100}
do
sed -i "s/(random<=.*)/(random<=$i)/g" myfile
done
Arash
Posted 2013-12-12T20:55:12.033
Reputation: 678
2
If you just want to match the number, you need positive lookbehind and lookahead. sed does not support this, but perl does.
perl -pi -e "s/(?<=\(random<=).*(?=\))/$i/g" myfile
To explain:
(?<= positive lookbehind
\(random<= match a literal (random<=
)
.* match any character, multiple times
(?= positive lookeahead
\) match a literal )
)
The lookbehind and lookahead matches are not used, so you can replace with $i.
slhck
Posted 2013-12-12T20:55:12.033
Reputation: 182 472
i think you are the father of linux :) – Arash – 2013-12-12T21:35:10.490
Problem solved! – Arash – 2013-12-12T22:08:27.770
@slhck i working with NS3 and ns3 is linux based simulator that use C++ file to build network. and every time i need o change some network parameter i need to change the c++ file(edit was made for question) – Arash – 2013-12-12T21:20:00.050
by the way i think this is not XY problem because the C++ file is just for building the results not for calculation and all af calculations done with shell scripting. could you plz help me with this? – Arash – 2013-12-12T21:24:23.147
1I know NS3. I think it'd be easier if you could just pass arguments to the C++ file instead. Anyway… what is the real question? Your script works, doesn't it? The only thing wrong with it is that it will always overwrite
myfileuntil you end up withrandom<=901at the last iteration. – slhck – 2013-12-12T21:25:43.810@slhck how could i replace just number? and what tool do you offer to me – Arash – 2013-12-12T21:26:48.763