parser.c

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include "parser.h"

//Global Variables
static const int BUFFER = 255;
static const int numFields = 15;
static const int stateField = 3;
static const int userField = 14;
static const int sysField = 15;
char *procDIR = "/proc/";
char *statDIR = "/stat";
char *statmDIR = "/statm";
char *cmdlineDIR = "/cmdline";

//Allocates memory for the process info and prints the output
int generatePrint(struct options *flags, int processID)
{
	struct info *pInfo = (struct info *) malloc(sizeof(struct info));
	initInfo(pInfo, processID);

	printf("%s: ", pInfo->pid);
	if (flags->s == ON && pInfo->state != '0')
		printf("%c ", pInfo->state);
	if (flags->U == OFF)
		printf("utime=%s ", pInfo->userTime);
	if (flags->S == ON && pInfo->systemTime != NULL)
		printf("stime=%s ", pInfo->systemTime);
	if (flags->v == ON && pInfo->vm != NULL)
		printf("size=%s ", pInfo->vm);
	if (flags->c == OFF && pInfo->cmdline != NULL)
		printf("[%s]", pInfo->cmdline);

	printf("\n");

	free(pInfo);
	return 0;
}

//Stores the process ID and calls the next three functions
void initInfo(struct info *pInfo, int processID)
{
	char pidStr[BUFFER];
	sprintf(pidStr, "%d", processID);
	pInfo->pid = pidStr;

	pInfo->state = '0';
	pInfo->userTime = NULL;
	pInfo->systemTime = NULL;
	pInfo->vm = NULL;
	pInfo->cmdline = NULL;

	parseStat(pInfo);
	parseStatm(pInfo);
	parseCmdline(pInfo);
}

//Parses /proc/<pid>/stat and stores the current state, 
//user time, and system time
void parseStat(struct info *pInfo)
{
	char buff[BUFFER];
	char fileLocation[BUFFER];
	char *p;
	strcpy(fileLocation, procDIR);
	strcat(fileLocation, pInfo->pid);
	strcat(fileLocation, statDIR);
	FILE * fp;
	fp = fopen(fileLocation, "r");
	int i = 0;
	if (fp != NULL)
	{
		while (i < numFields)
		{
			i++;	//at i of each field it stores corresponding value. 
			fscanf(fp, "%s", buff);
			if (i == stateField)
				pInfo->state = buff[0];
			if (i == userField)
			{
				p = (char*) malloc(sizeof(buff));
				strcpy(p, buff);
				pInfo->userTime = p;
				p = NULL;
			}
			if (i == sysField)
			{
				p = (char*) malloc(sizeof(buff));
				strcpy(p, buff);
				pInfo->systemTime = p;
				p = NULL;
			}
		}
		fclose(fp);
	}
}

//Parses /proc/<pid>/statm and stores the amount of
//virtual memory used
void parseStatm(struct info *pInfo)
{
	char buff[BUFFER];
	char fileLocation[BUFFER];
	char *p;
	strcpy(fileLocation, procDIR);
	strcat(fileLocation, pInfo->pid);
	strcat(fileLocation, statmDIR);
	FILE * fp;
	fp = fopen(fileLocation, "r");
	if (fp != NULL)
	{
		p = (char*) malloc(sizeof(buff));
		fscanf(fp, "%s", buff);
		strcpy(p, buff);	//vm is first value in file
		pInfo->vm = p;
		p = NULL;
		fclose(fp);
	}
}

//Parses the command line and stores the entire 
//command for a given pid
void parseCmdline(struct info *pInfo)
{
	char buff[BUFFER];
	char fileLocation[BUFFER];
	char *p;
	strcpy(fileLocation, procDIR);
	strcat(fileLocation, pInfo->pid);
	strcat(fileLocation, cmdlineDIR);
	FILE * fp;
	fp = fopen(fileLocation, "r");
	if (fp != NULL)
	{
		p = (char*) malloc(sizeof(buff));
		fgets(buff, sizeof buff, fp);
		strcpy(p, buff);	//if it's larger than buff, then that section is truncated.
		pInfo->cmdline = p;
		p = NULL;
		fclose(fp);
	}
	FILE *cmdline = fopen(fileLocation, "rb");
	char *arg = 0;
	size_t size = 0;
	p = (char*) malloc(sizeof(buff));
	while (getdelim(&arg, &size, 0, cmdline) != -1)
	{
		//puts(arg);
		strcat(p, arg);
		strcat(p, " ");
	}
	pInfo->cmdline = p;
	p = NULL;
	free(arg);
	fclose(cmdline);

}