C program to check whether file is empty or not
fp = fopen ("file1.txt",
"a+");
if (NULL != fp) {
fseek (fp, 0,
SEEK_END);
size = ftell(fp);
if (0 == size) {
printf("file is empty\n");
}
}
I am just a minute speck of negligible mass in the universe and yet, that doesn't stop me from exploring the fundamentals of technology.
C program to write structure values in file and read it back into another structure from the same file
C program to write structure values in file and read it back into another structure from the same file
#include<stdio.h>
struct Student {
char roll[5];
char name[12];
char percent[5];
char space;
} s1 = { "10",
"SMJC", "80", ' '};
int main() {
FILE *fp;
struct Student s2;
//Write details of
s1 to file
fp =
fopen("ip.txt", "w");
fwrite(&s1,
sizeof(s1), 1, fp);
fclose(fp);
fp =
fopen("ip.txt", "r");
fread(&s2,
sizeof(s2), 1, fp);
fclose(fp);
printf("\nRoll : %s", s2.roll);
printf("\nName : %s", s2.name);
printf("\nPercent : %s\n", s2.percent);
return (0);
}
C program to get system Uptime and print hrs, mins, day etc..
C program to get system Uptime and print hrs, mins, day etc..
/*
localtime example */
#include
<stdio.h>
#include
<time.h>
int
main ()
{
time_t rawtime;
struct tm * timeinfo;
int month_correction = 1;
int year_correction = 1900;
time ( &rawtime );
timeinfo = localtime ( &rawtime );
printf ( "\n Current local time and
date: %s \n", asctime (timeinfo) );
printf("\n Hour: %d",
timeinfo->tm_hour);
printf("\n Min: %d",
timeinfo->tm_min);
printf("\n Sec: %d",
timeinfo->tm_sec);
printf("\n Day: %d",
timeinfo->tm_mday);
printf("\n Month:
%ld",timeinfo->tm_mon + month_correction );
printf("\n year: %d",
timeinfo->tm_year + year_correction);
printf("\n");
return 0;
}
Output:
Current local time and date: Tue Mar 21 09:31:04 2017 Hour: 9 Min: 31 Sec: 4 Day: 21 Month: 3 year: 2017
C program to establish TCP/IP socket from one server machine to another client machine.
C program to establish TCP/IP socket from one server machine to another client machine
cat server.c
// Server side C program to demonstrate Socket programming#include <unistd.h>
#include <stdio.h>
#include <sys/socket.h>
#include <stdlib.h>
#include <netinet/in.h>
#include <string.h>
#include <arpa/inet.h>
#include <errno.h>
#include <netdb.h>
#include <sys/types.h>
#define PORT 8080
int get_locat_hostname_and_ip_address(char *local_hostname, char **ip_address)
{
struct hostent *host_entry;
int hostname;
// To retrieve hostname
hostname = gethostname(local_hostname, 256);
if (hostname == -1){
perror("gethostname");
return 1;
}
// To retrieve host information
host_entry = gethostbyname(local_hostname);
if (host_entry == NULL){
perror("gethostbyname");
return 1;
}
// To convert an Internet network address into ASCII string
*ip_address = inet_ntoa(*((struct in_addr*)host_entry->h_addr_list[0]));
if (NULL == *ip_address){
perror("inet_ntoa");
return 1;
}
printf("Hostname: %s\n", local_hostname);
printf("Host IP: %s\n", *ip_address);
return 0;
}
int main(int argc, char const *argv[])
{
int server_fd, new_socket, valread;
struct sockaddr_in address;
int opt = 1;
int addrlen = sizeof(address);
char buffer[1024] = {0};
char *hello = "Hello from server";
char host_name[256] = {0};
char *ip_address = NULL;
/************** Get hostname and Ip address *****************************/
get_locat_hostname_and_ip_address(host_name, &ip_address);
if (ip_address == NULL) {
printf("Server IP address is NULL\n");
exit(1);
}
// Creating socket file descriptor
//if ((server_fd = socket(AF_INET, SOCK_STREAM, 0)) == 0)
if ((server_fd = socket(AF_INET, SOCK_STREAM, 0)) == 0)
{
perror("socket failed");
exit(EXIT_FAILURE);
}
// Forcefully attaching socket to the port 8080
if (setsockopt(server_fd, SOL_SOCKET, SO_REUSEADDR | SO_REUSEPORT,
&opt, sizeof(opt)))
{
perror("setsockopt");
exit(EXIT_FAILURE);
}
address.sin_family = AF_INET;
//address.sin_addr.s_addr = INADDR_ANY;
address.sin_addr.s_addr = inet_addr(ip_address);
address.sin_port = htons( PORT );
// Forcefully attaching socket to the port 8080
if (bind(server_fd, (struct sockaddr *)&address,
sizeof(address))<0)
{
perror("bind failed");
exit(EXIT_FAILURE);
}
if (listen(server_fd, 3) < 0)
{
perror("listen");
exit(EXIT_FAILURE);
}
if ((new_socket = accept(server_fd, (struct sockaddr *)&address,
(socklen_t*)&addrlen))<0)
{
perror("accept");
exit(EXIT_FAILURE);
}
valread = read( new_socket , buffer, 1024);
printf("%s\n",buffer );
send(new_socket , hello , strlen(hello) , 0 );
printf("Hello message sent\n");
return 0;
}
cat client.c
// Client side C program to demonstrate Socket programming#include <stdio.h>
#include <sys/socket.h>
#include <stdlib.h>
#include <netinet/in.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#define PORT 8080
int main(int argc, char const *argv[])
{
struct sockaddr_in address;
int sock = 0, valread;
struct sockaddr_in serv_addr;
char *hello = "Hello from client";
char buffer[1024] = {0};
if ((sock = socket(AF_INET, SOCK_STREAM, 0)) < 0)
{
printf("\n Socket creation error \n");
return -1;
}
memset(&serv_addr, '0', sizeof(serv_addr));
serv_addr.sin_family = AF_INET;
serv_addr.sin_port = htons(PORT);
// Convert IPv4 and IPv6 addresses from text to binary form
if(inet_pton(AF_INET, "192.168.1.254", &serv_addr.sin_addr)<=0)
{
printf("\nInvalid address/ Address not supported \n");
return -1;
}
if (connect(sock, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) < 0)
{
printf("\nConnection Failed \n");
return -1;
}
send(sock , hello , strlen(hello) , 0 );
printf("Hello message sent\n");
valread = read( sock , buffer, 1024);
printf("%s\n",buffer );
return 0;
}
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