Functions from header files

Hi all,

I always think if we have a reference to all the C/C++ functions present in out system, it will be so much easier to write C programs with those functions. I posted this question to our ilugc, they introduced ‘ctags’ to me.

‘ctags’ is a simple utility which will produce a ‘ctags’ file which contains all definitions of macros, functions, structures, etc., If you want to know more about it, try ‘man ctags’.

The ‘ctags’ otuput file will be used by editors like vi, emacs to help developers to know about the syntex and function definiton.

I thought, It would be good if we can able to grep for functions, macros, from the ‘ctags’ file. Here is a simple script to achieve this task. Don’t forget to run,

$ ctags --verbose --recurse /usr/include

before executing this script. If you know better way to get reference to functions in our system, kindly share with me.

#!/bin/sh
#
# Description:
# program to search for functions, macros, definiton, etc.,
# in a 'ctags' file.
#
# Author: Mohan Raman
# License: Its in public domain, use it whatever way you want

USAGE="[USAGE]
	ctagsfilter.sh [-n tagname]  [-t tagtype] [-f headerfilename]
		[-h help] ctagsfile1 [ctagsfile2 ...]
"
HELP="${USAGE}
[DESCRIPTION]
	-n tagname		tag name to search
	-f headerfilename	header file to search
	-t tagtype		tag type, anyone of listed below
				c	class
				d	defined macro
				e	enum/enum member
				f	function
				g	global
				m	member of struct/class/enum/union
				n	namespace
				s	struct
				t	typedef
				u	union
				v	global variable
	-h			print this help
"

while getopts "n:t:f:h" OPTIONS
do
	case "${OPTIONS}" in
	n) TAGNAME="${OPTARG}";;
	t) TAGTYPE="${OPTARG}";;
	f) HEADER="${OPTARG}";;
	h) echo "${HELP}" && exit 0;;
	\?) echo "${USAGE}" && exit 1;;
	esac
done

shift $((OPTIND - 1))
test "${#}" -eq 0 && echo "${USAGE}" && exit 1

for FILE
do
	OUTPUTBUFFER=`cat "${FILE}"`

	if test ! -z "${TAGNAME}"
	then
		OUTPUTBUFFER=`echo "${OUTPUTBUFFER}" |
			awk -F' ' "\\$1 ~ /${TAGNAME}/{print \\$0;}"`
	fi

	if test ! -z "${HEADER}"
	then
		OUTPUTBUFFER=`echo "${OUTPUTBUFFER}" |
			awk -F'	' "\\$2 ~ /${HEADER}/{print \\$0;}"`
	fi

	if test ! -z "${TAGTYPE}"
	then
		OUTPUTBUFFER=`echo "${OUTPUTBUFFER}" |
			grep ";\"	${TAGTYPE}"`
	fi

	echo "${OUTPUTBUFFER}" 
done

Download : ctagsfilter.sh

‘localtime()’ loves ’05:30:00′

Hi friends,

Got some problem when I’m converting elapsed time ‘time_t’ to ‘struct tm’ for printing time in ‘%H:%M:%S” format. Here is the code,

/* code to learn how 'localtime()' works */

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

int main(int argc, char **argv)
{
	struct tm time1;
	struct tm *time2;
	time_t time;
	char timestring[20];

	time2 = (struct tm *)malloc(sizeof(struct tm));

	/* setting 0 seconds to time */
	time = (time_t) 0;
	localtime_r(&time, &time1);

	time1.tm_hour = time1.tm_hour - 5;
	time1.tm_min = time1.tm_min - 30;

	strftime(timestring,
		20,
		"%H:%M:%S",
		&time1);
	printf("Time1: %s\n",
		timestring);

	/* setting 1 minute 10 seconds to time */
	time = (time_t) 70;
	time2 = localtime(&time);

	time2->tm_hour = time2->tm_hour - 5;
	time2->tm_min = time2->tm_min - 30;

	strftime(timestring,
		20,
		"%H:%M:%S",
		time2);
	printf("Time2: %s\n",
		timestring);

	free(time2);
	return(0);
}

And the output is,

Time1: 05:30:00
Time2: 05:31:10

I don’t know why its happening, ‘localtime()’ creates ‘struct tm’ structure which by default have 05:30:00 as its starting time. I need to manually subtract the 5 from tm_hour and 3 from tm_min to get what I want.

	time1.tm_hour = time1.tm_hour - 5;
	time1.tm_min = time1.tm_min - 30;

	time2->tm_hour = time2->tm_hour - 5;
	time2->tm_min = time2->tm_min - 30;

Here is the updated output,

Time1: 00:00:00
Time2: 00:01:10

Also ‘localtime()’ sets default values to all the variables in the result ‘struct tm’ structure. google not helping to find the reason.