UNIX for Dummies Questions & Answers

hello world, i was looking for exemples for writing ans reading in / from a file, more exactly a text file; and how i'm only at very beagining, if anyone have some exemples very simple, very 'classic' , -with explications- and not hard to undersand . i was wondering that some of you are theacher and meet this problem frequent ,or just you may have some answers near. thank you and scuze my bad english.

What are you looking to do this in? A shell(i.e. ksh, bash, etc), perl, c, java, etc. from a database(i.e. oracle, db2, etc)?

well , i know how to do it in c , c++ and java and is pretty easy, what i don't undersandd are the shell comandes ,it looks like c but a little more absatract (so far), and therefore i'm looking for exemples with some explanations for comandes

What shell are you using? what is your OS?

linux; now i'm using ubuntu instaled on windows and i sure hope that don't make me any problem

---------- Post updated at 02:28 AM ---------- Previous update was at 02:26 AM ----------

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

union semun {
int val; /* Value for SETVAL */
struct semid_ds *buf; /* Buffer for IPC_STAT, IPC_SET */
unsigned short *array; /* Array for GETALL, SETALL */
struct seminfo *__buf; /* Buffer for IPC_INFO
(Linux-specific) */
};

int main(int argc, char *argv[])
{
FILE *out;
int i;
int mutex, empty, full;
char buffer_sir_citit [100];
struct sembuf sem_down, sem_up;



mutex = semget(26, 1, 0666 | IPC_CREAT | O_EXCL);
if (mutex <= 0)
{
if (errno == EEXIST) mutex = semget(1356, 1, 0666);
else
{printf("fail to get semaphore"); exit(1);}
}
else
{
union semun sem_union;
sem_union.val = 1;
if (semctl(mutex, 0, SETVAL, sem_union) == -1)
{
printf("nu s-a initializat mutex \n");
return(1);
}
}

empty = semget(35, 1, 0666 | IPC_CREAT | O_EXCL);
if (empty <= 0)
{
if (errno == EEXIST) empty = semget(1356, 1, 0666);
else
{printf("fail to get semaphore"); exit(1);}
}
else
{
union semun sem_union;
sem_union.val = 1;
if (semctl(empty, 0, SETVAL, sem_union) == -1)
{
printf("nu s-a initializat empty \n");
return(1);
}
}

full = semget(42, 1, 0666 | IPC_CREAT | O_EXCL);
if (full <= 0)
{
if (errno == EEXIST) full = semget(1356, 1, 0666);
else
{printf("fail to get semaphore"); exit(1);}
}
else
{
union semun sem_union;
sem_union.val = 0;
if (semctl(full, 0, SETVAL, sem_union) == -1)
{
printf("nu s-a initializat full \n");
return(1);
}
}


sem_down.sem_num = 0;
sem_down.sem_op = -1; /* P() */
sem_down.sem_flg = SEM_UNDO;

sem_up.sem_num = 0;
sem_up.sem_op = 1; /* P() */
sem_up.sem_flg = SEM_UNDO;

while (1)
{
scanf("%s\n", buffer_sir_citit);
semop(empty, &sem_down, 1);
semop(mutex, &sem_down, 1);
out = fopen("file.out","w");

if (out<0)
{
printf("Nu exista fisierul \n");
exit(1);
}
fprintf(out, "%s\n", buffer_sir_citit);
fclose(out);

semop(mutex, &sem_up, 1);
semop(full, &sem_up, 1);
}


}



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

union semun {
int val; /* Value for SETVAL */
struct semid_ds *buf; /* Buffer for IPC_STAT, IPC_SET */
unsigned short *array; /* Array for GETALL, SETALL */
struct seminfo *__buf; /* Buffer for IPC_INFO
(Linux-specific) */
};

int main()
{

FILE *out;
int i;
int mutex, empty, full;
char buffer_sir_citit [100];
struct sembuf sem_down, sem_up;



mutex = semget(26, 1, 0666 | IPC_CREAT | O_EXCL);
if (mutex <= 0)
{
if (errno == EEXIST) mutex = semget(1356, 1, 0666);
else
{printf("fail to get semaphore"); exit(1);}
}
else
{
union semun sem_union;
sem_union.val = 1;
if (semctl(mutex, 0, SETVAL, sem_union) == -1)
{
printf("nu s-a initializat mutex \n");
return(1);
}
}

empty = semget(35, 1, 0666 | IPC_CREAT | O_EXCL);
if (empty <= 0)
{
if (errno == EEXIST) empty = semget(1356, 1, 0666);
else
{printf("fail to get semaphore"); exit(1);}
}
else
{
union semun sem_union;
sem_union.val = 1;
if (semctl(empty, 0, SETVAL, sem_union) == -1)
{
printf("nu s-a initializat empty \n");
return(1);
}
}

full = semget(42, 1, 0666 | IPC_CREAT | O_EXCL);
if (full <= 0)
{
if (errno == EEXIST) full = semget(1356, 1, 0666);
else
{printf("fail to get semaphore"); exit(1);}
}
else
{
union semun sem_union;
sem_union.val = 0;
if (semctl(full, 0, SETVAL, sem_union) == -1)
{
printf("nu s-a initializat full \n");
return(1);
}
}


sem_down.sem_num = 0;
sem_down.sem_op = -1; /* P() */
sem_down.sem_flg = SEM_UNDO;

sem_up.sem_num = 0;
sem_up.sem_op = 1; /* P() */
sem_up.sem_flg = SEM_UNDO;

while (1)
{
semop(full, &sem_down, 1);
semop(mutex, &sem_down, 1);

out = fopen("file.out","r");

if (out<0)
{
printf("Nu exista fisierul \n");
exit(1);
}

fscanf(out, "%s\n", &buffer_sir_citit);
fclose(out);

semop(mutex, &sem_up, 1);
semop(empty, &sem_up, 1);

printf("%s\n", buffer_sir_citit);
}
}

---------- Post updated at 02:30 AM ---------- Previous update was at 02:28 AM ----------

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

union semun {
int val; /* Value for SETVAL */
struct semid_ds *buf; /* Buffer for IPC_STAT, IPC_SET */
unsigned short *array; /* Array for GETALL, SETALL */
struct seminfo *__buf; /* Buffer for IPC_INFO
(Linux-specific) */
};
int main(int argc, char *argv[])
{

int s;
struct sembuf sem_b;



s = semget(1356, 1, 0666 | IPC_CREAT);

union semun sem_union;
sem_union.val = 1;
if (semctl(s, 0, SETVAL, sem_union) == -1)
{
printf("Nu exista fisierul \n");
return(1);
}

exit(0);
}


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

int main(int argc, char *argv[])
{
FILE *out;
int i;

out = fopen("file.out","w");

if (argc>1)
for (i=1; i<argc; i++)
fprintf(out, "%s\n", argv[i]);

fclose(out);

exit(0);
}


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

union semun {
int val; /* Value for SETVAL */
struct semid_ds *buf; /* Buffer for IPC_STAT, IPC_SET */
unsigned short *array; /* Array for GETALL, SETALL */
struct seminfo *__buf; /* Buffer for IPC_INFO
(Linux-specific) */
};

int main(int argc, char *argv[])
{
int fisier;
int i;
int s;
struct sembuf sem_b;



s = semget(1356, 1, 0666 | IPC_CREAT);


sem_b.sem_num = 0;
sem_b.sem_op = -1; /* P() */
sem_b.sem_flg = SEM_UNDO;
if (semop(s, &sem_b, 1) == -1)
{
fprintf(stderr, "semaphore_p failed\n");
return(1);
}


fisier = open("file.out", O_WRONLY);

if (fisier<0)
{
printf("Nu exista fisierul \n");
exit(1);
}

if (argc>1)
for (i=1; i<argc; i++)
{
write(fisier, argv[i], strlen(argv[i]));
write(fisier, "\n", 1);
}

close(fisier);


exit(0);

}

This is some info showing some examples and references:
Korn shell scripting
Bash Reference Manual
Ksh Read a File Line By Line ( UNIX Scripting )
Reading Multiple Files with Bash | Linux Journal

Not to forget one of our classics:

12 ways to parse a file

I hope this helps.

bakunin