Hajdúbagosi SportegyesületHajrá Hajdúbagos!
Alacsony I/O
#include<unistd.h>
#include<sys/stat.h>
#include<fcntl.h>
#include<stdio.h>
#define N 100
int main(int argc, char *argv[]){
char T[N];
int x;
if (argc<3){
fprintf(stderr,"keves argumentum");
return 1;
}
int be = open(argv[1],O_RDONLY);
int ki = open(argv[2],O_WRONLY| O_CREAT| O_TRUNC| S_IRUSR|S_IWUSR|S_IRGRP|S_IROTH);
while((x=read(be,T,N))>0)
write(ki,T,x);
close(be);
close(ki);
}
--------------------------------------------
Formázott I/O
#include<stdio.h>
int main(){
int pos;
char c, text[100];
FILE *f;
// Opening file
f=fopen("file.txt","w+");
if(f==NULL){
fprintf(stderr," There is a file opening problem!\n");
return 1;
}
// Write the file
fprintf(stdout," What word would you like to write into the file?\n ");
fscanf(stdin,"%s",text);
fprintf(f,"%s",text);
// Positioning and rewriting
fprintf(stdout," Let's owerwrite something!\n From which character? Give a number! ");
fscanf(stdin,"%d",&pos);
fprintf(stdout," What is the new text? ");
fscanf(stdin,"%s",text);
fseek(f,pos-1,SEEK_SET);
fprintf(f,"%s",text);
// Reading the file
fprintf(stdout," Now the file contetnt is:\n ");
fseek(f,0,SEEK_SET);
while(1){
fscanf(f,"%c",&c);
if(feof(f)) break;
fprintf(stdout,"%c",c);
}
// Closing the file
fclose(f);
return 0;
}
--------------------------------------------------
/*** Listing a directory ***/
#include<stdio.h>
#include<stdlib.h>
#include<dirent.h>
int main(){
DIR *d;
struct dirent *entry;
d=opendir(".");
printf(" -my ls:\n");
entry=readdir(d);
while(entry!=NULL){
if((*entry).d_name[0]!='.')
printf("%s ",(*entry).d_name);
entry=readdir(d);
}
closedir(d);
printf("\n -system ls:\n");
chdir(".");
system("ls");
return 0;
}
------------------------------------
/*** Example of inode reading ***/
#include<stdio.h>
#include<sys/stat.h>
#include<time.h>
int main(int argc, char* argv[]){
struct stat inode;
if(argc==1) {
fprintf(stderr," File or directory name is necessary");
return 1;
}
stat(argv[1],&inode);
printf(" \"%s\" is a %s.\n",argv[1],(inode.st_mode&S_IFDIR)?"directory":"file");
-----------------------------------------------
/*** Using temporary file ***/
#include <stdio.h>
int main(){
char tmpname[L_tmpnam];
char text[100];
char *filename;
FILE *tmpfp;
filename = tmpnam(tmpname);
printf("A temporary file name is: %s\n", tmpname);
tmpfp = tmpfile();
if(tmpfp){
fprintf(tmpfp,"It_is_not_importanat.\n");
fseek(tmpfp,0L,SEEK_SET);
fscanf(tmpfp,"%s",text);
printf("Tempfile contains: %s\n",text);
fclose(tmpfp);
}
else
printf("Temporary file problem!\n");
return 0;
}
-----------------------------------------------
/*** Example of fork ***/
// gcc -o fork fork.c
#include<stdio.h>
#include<stdlib.h>
#include<unistd.h>
int main(){
int x=0;
pid_t pid;
fprintf(stdout,"Start... x=%d\n",x);
pid=fork();
if(pid==0){ // Child
x=1;
fprintf(stderr,"Child... x=%d (PID=%d, parent is %d)\n",x,getpid(),getppid());
sleep(2); // Child is working...
fprintf(stderr,"Child ps:\n");
system("ps -al |grep fork >&2");
sleep(2);
fprintf(stderr,"End child. (PID=%d)\n",getpid());
return 0;
}
else{ // Parent
x=2;
fprintf(stdout,"Parent... x=%d (PID=%d)\n",x,getpid());
sleep(6); // Parent is working...
fprintf(stdout,"Paternt ps:\n");
system("ps -al |grep fork");
sleep(2);
fprintf(stdout,"End parent. (PID=%d)\n",getpid());
return 0;
}
}
------------------------------------------------------------
/*** Signal catch ***/
#include<stdio.h>
#include<signal.h>
#include<unistd.h>
void jajj(int sig){
printf("\n Jajj!\n");
signal(SIGINT, SIG_DFL); // back to default signal handling
}
int main(){
int i;
signal(SIGINT, jajj);
printf("Start...\n");
for(i=1;i<=10;i++){
sleep(1);
printf(" sleeptime: %d s\n",i);
}
return 0;
}
----------------------------------
/*** Signal sending ***/
#include<stdio.h>
#include<signal.h>
#include<unistd.h>
#include<sys/wait.h>
static int isListen=0;
void listen(int sig){
isListen=1;
}
int main(){
pid_t pid;
pid=fork();
if(pid==0){ // child
printf(" Child: I am working.\n");
sleep(6); // Child is working
printf(" Child: I am ready.\n");
kill(getppid(),SIGUSR1);
}
else { // parent
printf(" Parent: I am working.\n");
sleep(3); // Parent is working
signal(SIGUSR1,listen);
printf(" Parent: I am waiting for Child's results.\n");
pause();
if(isListen==1)
printf(" Parent: I continue my work.\n");
else{
printf(" Parent: I got a signal, but not SIGUSR1.\n");
return 2;
}
sleep(3);
printf(" The End.\n");
}
return 0;
}
---------------------------------------------------
/*** Synchronizing by SIGUSR1 signal sending ***/
#include<stdio.h>
#include<signal.h>
#include<unistd.h>
#include<sys/wait.h>
static int isListen=0;
void listen(int sig){
isListen=1;
}
void nolisten(){
isListen=0;
}
int main(){
pid_t pid;
pid=fork();
if(pid==0){ // child
printf(" Child: I am working.\n");
sleep(6); // Child is working
printf(" Child: I am ready.\n");
kill(getppid(),SIGUSR1);
sleep(3); // Child is working
signal(SIGUSR1,listen);
printf(" Child: I am waiting for Parent.\n");
pause();
if(isListen==1)
printf(" Child: I continue my work.\n");
else{
printf(" Child: I got a signal, but not SIGUSR1.\n");
return 1;
}
sleep(6); // Child is working
printf(" Child: I am ready.\n");
}
else { // parent
printf(" Parent: I am working.\n");
sleep(3); // Parent is working
signal(SIGUSR1,listen);
printf(" Parent: I am waiting for Child.\n");
pause();
if(isListen==1)
printf(" Parent: I continue my work.\n");
else{
printf(" Parent: I got a signal, but not SIGUSR1.\n");
return 2;
}
nolisten();
sleep(6); // Parent is working
printf(" Parent: I am ready.\n");
kill(pid, SIGUSR1);
sleep(3);
printf(" Parent: I am ready.\n");
wait(NULL); // Parent wait for Child end
printf(" The End.\n");
}
return 0;
}
---------------------------------------
/*** Example of alarm function and SIGALRM signal. ***/
#include<stdio.h>
#include<stdlib.h>
#include<signal.h>
#include<unistd.h>
void end(int sig){
fprintf(stderr,"\n Sorry, time out!\n");
exit(1);
}
int main(){
int a;
signal(SIGALRM,end);
alarm(5);
printf(" Write an integer number within 5 seconds: ");
scanf("%d",&a);
printf(" The number is: %d\n",a);
return 0;
}
------------------------------------
/*** Signal catch ***/
#include<stdio.h>
#include<signal.h>
#include<unistd.h>
void jajj(int sig){
printf("\n Jajj!\n");
signal(SIGINT, SIG_DFL); // back to default signal handling
}
int main(){
int i;
signal(SIGINT, jajj);
printf("Start...\n");
for(i=1;i<=10;i++){
sleep(1);
printf(" sleeptime: %d s\n",i);
}
return 0;
}
----------------------------------
*** Pseudo-random numbers ***/
#include<stdio.h>
#include<stdlib.h>
#include<time.h>
#define N 1000000
int main(){
int i;
int x;
int a[6]={0,0,0,0,0,0};
srand(time(NULL));
printf("0<=%d<=%d\n",rand(),RAND_MAX);
printf("0.000000<=%f<=1.000000\n",(float)rand()/RAND_MAX);
printf("Dice (%d throw):\n",N);
for(i=0;i<N;i++){
do
x=rand();
while(x>=RAND_MAX-RAND_MAX%6); // To ensure equal probability
a[x%6]++;
}
for(i=0;i<6;i++)
printf("%d:\t%.4f%%\n",i+1,(float)a[i]/N*100);
return 0;
}
----------------------------------------------------
int main (int argc, char *argv[]){
if (argc == 1){
fprintf (stderr, "Keves argumentum!\n");
}
srand (time(NULL));
struct dirent *entry;
char T[100], c, T2[100];
struct stat inode;
DIR *d;
FILE *f;
int random = rand()%57+65;
printf ("%c\n", random);
d = opendir(".");
entry = readdir(d);
while (entry != NULL){
if ((*entry).d_name[0] != '.')
printf ("%s ", (*entry).d_name);
entry=readdir(d);
}
printf ("\n");
closedir(d);
fprintf (stdout,"Kerek egy file vagy konyvtar nevet: ");
fscanf (stdin, "%s", T);
stat (T, &inode);
printf ("%s is a %s\n", T, (inode.st_mode&S_IFDIR) ? "Directory" : "File");
while(1){
if (inode.st_mode&S_IFDIR){
d = opendir (T);
chdir (T);
entry = readdir(d);
while (entry != NULL){
if ((*entry).d_name[0] != '.')
printf ("%s ", (*entry).d_name);
entry = readdir(d);
}
closedir(d);
fprintf (stdout, "\nKerek egy nevet: ");
fscanf (stdin, "%s", T);
stat(T, &inode);
printf ("%s is a %s\n", T, (inode.st_mode&S_IFDIR) ? "Directory" : "File");
continue;
}//Ifvége
else{
f = fopen (T, "r");
while(1){
fscanf (f, "%c", &c);
titkosit (c);
if (feof(f)) break;
fprintf (stdout, "%c", c);
}
break;
}//Else vége
}//While vége
}
----------------------------------------------------
//Felkialtojel az utolso karakter helyén alacsony szintu fajlkezelessel
#include <stdlib.h>
#include <stdio.h>
#include <time.h>
#include <math.h>
#include <string.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <unistd.h>
#include <dirent.h>
#include <signal.h>
#define N 1000
int main(int argc, char* argv[]){
int f = open ("PID.txt", O_RDWR);
char buffer[N];
int nread, i;
while ((nread = read(f, buffer,N))>0)
close(f);
for (i = strlen(buffer);i >=0; i--){
if ((buffer[i] >= 'a' && buffer[i] <='z') || (buffer[i] >= 'A' && buffer[i] <= 'Z')){
buffer[i] = '!';
f = open ("PID.txt", O_TRUNC | O_RDWR);
write (f, buffer, strlen(buffer));
break;
}
}
close(f);
return 0;
}//main
--------------------------------------
//8. Írj egy C programot, amiben egy szülonek két gyerek folyamata van és a késobb létrejött gyerek írja ki a korábbi PID-jét! (öccs a bátyó pidjét)
#include <stdlib.h>
#include <stdio.h>
#include <time.h>
#include <math.h>
#include <string.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <unistd.h>
#include <dirent.h>
#include <signal.h>
#define N 1000
int main(int argc, char* argv[]){
pid_t pid, pid2;
pid = fork();
if (pid == 0){
printf ("Batyj: %d\n", getpid());
return 0;
}
else{
pid2 = fork();
if (pid2 == 0){
printf ("Ocsi Batyj Pid-je: %d\n", pid);
return 0;
}
printf ("Szulo pid: %d\n", getpid());
}
return 0;
}//main
----------------------------------------------
//6. Írj egy C programot, amely két részbol áll. A program 1 másodpercenként kiírja az A betut, Ctrl+C hatására pedig a B betut, ugyanúgy 1 másodpercenként.
#include <stdlib.h>
#include <stdio.h>
#include <time.h>
#include <math.h>
#include <string.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <unistd.h>
#include <dirent.h>
#include <signal.h>
#define N 1000
static int listen = 0;
void b (int s){
signal (SIGINT, SIG_DFL);
while(1){
printf ("B\n");
sleep(1);
}
}
int main(int argc, char* argv[]){
int i;
signal (SIGINT, b);
while(1){
printf ("A\n");
sleep(1);
}
return 0;
}//main
+++++++++++++++++++++++++++++++++++++++++++++
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <time.h>
#include <signal.h>
#include <fcntl.h>
#include <sys/stat.h>
void change(int pid){
FILE *g = fopen("temp.txt","w");
fprintf(g,"B");
fclose(g);
signal(SIGINT,SIG_DFL);
}
int main(){
char c[1024];
int f;
signal(SIGINT,change);
while(1){
f=open("temp.txt",O_RDONLY);
read(f,c,1024);
close(f);
printf("%s",c);
sleep(1);
}
return 0;
}
----------------------------------------------
//feladat2: irj egy olyan programot ami letrehoz egy gyerekfolyamatot, a gyerekfolyamat pedig meg egy gyerekfolyamatot, es ez utobbi irja ki a nagyapjanak a pidjet, azaz az unoka irja ki a nagyapja pidjett
#include <stdlib.h>
#include <stdio.h>
#include <time.h>
#include <math.h>
#include <string.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <unistd.h>
#include <dirent.h>
#include <signal.h>
#define N 1000
static int listen = 0;
void islisten(int s){
listen = 1;
}
void bezar (int s){
printf ("Bezarom a programot!\n");
kill(getppid(), SIGKILL);
}
int main(int argc, char* argv[]){
pid_t pid, pid2;
pid = fork();
FILE *f;
int d;
if (pid == 0){
signal (SIGUSR1, islisten);
pause();
if (listen){}
pid2 = fork();
if (pid2 == 0){
f = fopen ("PID2.txt", "r");
fscanf (f, "%d",&d);
fprintf (stdout,"Papa PID-je: %d\n", d);
fclose(f);
return 0;
}
else{return 0;}
}
else{
f = fopen ("PID2.txt","w+");
fprintf (f, "%d", getpid());
fclose(f);
kill(pid,SIGUSR1);
}
return 0;
}//main
-------------------------------------------------------
//Terminalt bezarja megszakitas kiadasakor
#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <unistd.h>
void megszakitas(int pid){
printf("\nMegszakitas erkezett\n");
alarm(0);
kill(getppid(),SIGKILL);
}
void timeout(int pid){
printf("Az ido lejart!\n");
exit(1);
}
int main(int argc, char** argv){
int i;
signal(SIGINT, megszakitas);
signal(SIGALRM, timeout);
printf("Visszaszamolok 5 masodpercrol!\n");
alarm(5);
for(i=5;i>=1;i--) {
printf("%d. s\n",i);
sleep(1);
}
return 0;
}
-------------------------------------------------------------
//Legkisebb file-t megkeressuk az aktualis konyvtarban majd hozzafuzunk egy szoveget
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/stat.h>
#include <dirent.h>
#include <string.h>
int main(int argc, char** argv){
int min=0xFFFFFF;
char t[40];
struct dirent *entry;
struct stat inode;
DIR *d = opendir(".");
entry=readdir(d);
while(entry!=NULL){
stat((*entry).d_name,&inode);
if((inode.st_mode & S_IFDIR)==0 && strstr((*entry).d_name,".txt\0") && !strstr((*entry).d_name,".txt~\0"))
if(inode.st_size<=min){
min=inode.st_size;
strcpy(t,(*entry).d_name);
}
entry=readdir(d);
}
closedir(d);
FILE *f = fopen(t,"a");
fprintf(f,"\nEzt a szoveget fuzom hozza a dokumentumhoz.\n");
fclose(f);
printf("%s \t %d\n",t,min);
return 0;
}
-----------------------------------------------
//Karakterszámolás alacsony szinten
int main(int argc, char* argv[]){
int f = open ("PID.txt", O_RDWR);
int nread,i;
char buffer[N];
while ((nread = read (f, buffer, N))>0){
write (1, buffer, nread);
}
for (i= strlen(buffer); i>=0; i--)
write(1,&(buffer[i]),sizeof(char));
close (f);
}//main
----------------------------------------------
//3. Írj egy C programot, amely egy létezo file tartalmát visszafelé a képernyore íratja!
#include <stdlib.h>
#include <stdio.h>
#include <time.h>
#include <math.h>
#include <string.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <unistd.h>
#include <dirent.h>
#include <signal.h>
#define N 1000
static int listen = 0;
int main(int argc, char* argv[]){
FILE *f = fopen ("PID.txt", "r+");
int i = 0;
char c, d;
while (1){
fscanf (f,"%c", &c);
i++;
if (feof(f)) break;
fprintf (stdout,"%c", c);
}
fprintf (stdout,"\ni = %d\n", i);
fseek (f,i,SEEK_SET);
while (i>-1){
fscanf (f, "%c", &d);
fprintf (stdout, "%c", d);
i--;
fseek(f, i, SEEK_SET);
}
fprintf (stdout,"\n");
fclose(f);
return 0;
}//main
---------------------------------------
9. Írj egy C programot, amely a parancssori argumentumban megadott létezo fájl nevét
beolvassa és alacsony szintu fájlkezeléssel törli a fájl tartalmát, de magát a fájlt nem!
...
int in = open (argv[1], O_TRUNC|O_RDWR);
close (in)
....
----------------------------------------