Shell Programming and Scripting

#!/bin/ksh
# test.sh

old="0"
while true
do
     echo "`last_written /tmp/filename EXACTO  $old`" | read old lines         
     if [ $old -lt 0 ] ; then
         echo "Error opening file"
         exit
     fi
     echo "$lines lines found `date +%c` "    
     sleep 5
done

/******************************************************************
*
* last_written.c  
*  usage: last_written <filename> <search string> <last byte>
*                      
*                      
*  output  <total bytes searched> <total new lines with search string>
*  assumes:
*           searchstr occurs 0 or 1 times in a line only
*           filename is a carriage control file
*  prints -1 -1 to stdout on failure 
*******************************************************************/

#include <sys/types.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <fcntl.h>
#include <sys/stat.h>

void usage(void)
{
    fprintf(stdout,"-1 -1 \n");
    fprintf(stderr," usage: last_written <filename> <search string> <last byte>	\n");
    exit(EXIT_FAILURE);
}

/* file close routine */
void closeit(int fd)
{
    if (close(fd)== (-1))
    {
    	fprintf(stdout,"-1 -1 \n");    	
        perror("Error opening input file");
        exit(EXIT_FAILURE);
    }	
}

/* count occurrences of searchstr in a buffer */
int find(char *buf, char *searchstr)
{
    int result = 0;
    char *p=NULL;
    
    p=strstr(buf,searchstr);
    while(p!=NULL)
    {        
        result++;
        p++;
        p=strchr(p,'\n');
        if(p!=NULL)
        {
        	p=strstr(p,searchstr);
        }
    }
    return result;
}

/* read nbytes from a file */
ssize_t readall(int fd, void *buf, size_t nbyte)
{
    ssize_t nread = 0, n=0; 

    do 
    {
        if ((n = read(fd, &((char *)buf)[nread], nbyte - nread)) == -1) 
        {
            if (errno == EINTR)
            {
                continue;
            }
            else
            {
                return (-1);
            }
        }
        if (n == 0)
        {
            return nread;
        }
        nread += n;
    } while (nread < nbyte);
    return nread;
}


int main(int argc, char *argv[])
{
    int fd=0;                      /* file descriptor */
    struct stat st;                /* stat structure for file size */  
    char *p=NULL;                  /* pointer into the file */
    char *buf=NULL;                /* holds file */
    ssize_t bytes=0;               /* bytes read from the file */
    long file_pos=0;               /* starting offset into file */
    long lines=0;                  /* number of new lines to search */
    long result=0;                 /* number of lines with searchstr */
    
    if(argc!=4) usage();          /* exit on bad parameters */
    
    fd=open(argv[1],O_RDONLY);
    if( fd< 0 || fstat(fd,&st) == (-1) )
    {
        fprintf(stdout,"-1 -1\n");  /* -1 is error */
        perror("Error opening input file");
        exit(EXIT_FAILURE);
    }    
    if(st.st_size==atol(argv[3]) ) /* old file size == new file size */
    {
        fprintf(stdout,"%10s %10d\n", argv[3],0);
        exit(EXIT_SUCCESS);
    }
    buf=malloc(st.st_size+ 1);     /*create a buffer to hold the file */
    if(buf==NULL)
    {
    	fprintf(stdout,"-1 -1 \n");
        perror("Error allocating memory");
        exit(EXIT_FAILURE);
    }
    memset(buf,0x0,st.st_size+1);
    bytes=readall(fd,buf,st.st_size);
    if(bytes==(-1))
    {
    	fprintf(stdout,"-1 -1 \n");    	
        perror("Error reading file");
        exit(EXIT_FAILURE);
    }
        
    /* start looking where we left off before */
    p=buf;
    p+=atol(argv[3]);
    bytes=st.st_size;
    if(*p)
    {                           
        result=find(p,argv[2]); /*count the number of lines with searchstr */
    }
    closeit(fd);
    free(buf);
    /*  output  <total bytes searched so far> <total new lines with search string> */
    fprintf(stdout,"%10d %10d\n",bytes,result);
    return 0;
}

kcsdev:/home/jmcnama> lastw.sh
7 lines found Mon Jun 20 12:47:06 2005
2 lines found Mon Jun 20 12:47:11 2005
2 lines found Mon Jun 20 12:47:16 2005
1 lines found Mon Jun 20 12:47:21 2005
2 lines found Mon Jun 20 12:47:26 2005
1 lines found Mon Jun 20 12:47:31 2005
3 lines found Mon Jun 20 12:47:36 2005