Regular expression to extract header name from c file

Question

How to extract headers from a c file that contains them like this?

#include <tema4header9.h>
#include    <tema4header3.h>
#include   <stdio.h>
#include        <longnametest/newheader.h>
#include <net/header.h>
#include  "last-test-Zhy3/DrRuheader.h"
#include <last-test-8fF7/a5xyheader.h>

I tried to use:

sed -n -e 's/#include[ \t]*[<"]\([^ \/<"]*\/[^ \/]*\)\.h[">]/\1\.h/p'

but it only works for those in subdirectories. also if i type:

sed -n -e 's/#include[ \t]*[<"]\(([^ \/<"]*\/)+[^ \/]*\)\.h[">]/\1\.h/p'

or

sed -n -e 's/#include[ \t]*[<"]\(([^ \/<"]*\/)*[^ \/]*\)\.h[">]/\1\.h/p'

the command does not work anymore. The output file should look like this:

tema4header9.h
tema4header3.
stdio.h
longnametest/newheader.h
net/header.h
last-test-Zhy3/DrRuheader.h
last-test-8fF7/a5xyheader.h

What is your expected output? `tema4header9.h`, etc.. ? – Inian Dec 23 '16 at 09:03 — Inian, Dec 23 '16 at 09:03

P.... · Accepted Answer · 2016-12-23T09:20:58.273

2

grep solution: This is using perl regex and printing anything between "<" or '"' on the lines which start with #include.

grep -oP '^#include.*(<|")\K.*(?=>|")' headers
tema4header9.h
tema4header3.h
stdio.h
longnametest/newheader.h
net/header.h
last-test-Zhy3/DrRuheader.h
last-test-8fF7/a5xyheader.h

If you are ok with awk:

awk '/#include/{gsub(/<|>|"/,"",$2);print $2}' headers
tema4header9.h
tema4header3.h
stdio.h
longnametest/newheader.h
net/header.h
last-test-Zhy3/DrRuheader.h
last-test-8fF7/a5xyheader.h

edited Dec 23 '16 at 09:20

answered Dec 23 '16 at 09:10

P....

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Just `'(?<="|\)'` is suffiicient for `grep` – Inian Dec 23 '16 at 09:33
@Inian than it might extract some data from undesired line in the `file.c` like `cout << "hey there" << "x>y" < – P.... Dec 23 '16 at 09:39
I meant for the part to extraction within quotes and ` – Inian Dec 23 '16 at 09:41
Can anybody tell me how to write the above grep like regex for C++ regex_search ? – Aditya kumar May 30 '20 at 19:07
Warning: these patterns do not capture all `#include`. Spacing and tabs are allowed around the `#` in C/C++. E.g. `# include `. Correct: `grep -oE '^[ \t]*#[ \t]*include[ \t]*(|"[^"]*")' headers` – Dr. Alex RE Aug 17 '21 at 14:01

score 1 · Answer 2 · answered Dec 23 '16 at 09:08

1

This should work:

sed -nr 's/#include\s+[<"]([^>"]+)[>"].*/\1/p'

answered Dec 23 '16 at 09:08

klarsen

11
3

score 0 · Answer 3 · answered Dec 23 '16 at 09:46

0

Try:

awk '{match($0,/[<"].*[>"]/);print substr($0,RSTART+1,RLENGTH-2)}' Input_file

answered Dec 23 '16 at 09:46

RavinderSingh13

117,272
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Li-Guangda · Answer 4 · 2021-08-15T03:00:21.100

0

Like above:

sed -n 's/\s*#\s*include\s*[<"]\(.\+.h\)[>"]/\1/p' input_file

but it is more precise, for example, the input_file content is:

 # include <stdio.h>
       #        include<stdlib.h>
    #    include    <time.h>
 #define LEN 8
 #define OPT 2
 #include <pthread.h>
 # include "mysql.h"
 #include "paths.h"

it can still print right:

stdio.h
stdlib.h
time.h
pthread.h
mysql.h
paths.h

edited Aug 15 '21 at 03:00

answered Aug 15 '21 at 02:53

Li-Guangda

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Regular expression to extract header name from c file

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