read function never return 0 in C
I'm trying to read float values through a pipe as long as there is data in it. The problem is that the read function never returns 0 in my case, so my function never gets out of the loop.
Moreover, I cannot use library functions.
To give you the context : I want to create child processes which run the following function. Each float value is sent by the parent through the pipe and is read by one of the children processes which is supposed to sleep in order to let another child process read 1 other value and sleep. When a process wakes up, he's supposed to check if it can get a value from the pipe to sleep again, otherwise the loop ends and the child process is exited.
void worker(int * pip){
close(pip[1]);
float buffer;
while(read(pip[0], &buffer, sizeof(float)) != 0){
sleep(buffer);
}
exit(1);
}
Each value is written by the parent this way in a loop :
write(pip[1], &values[i], sizeof(float))
c pipe
edited Nov 26 '18 at 10:28
Sourav Ghosh
111k15132191
asked Nov 26 '18 at 10:14
Arthur KlipfelArthur Klipfel
2118
add a comment |
I'm trying to read float values through a pipe as long as there is data in it. The problem is that the read function never returns 0 in my case, so my function never gets out of the loop.
Moreover, I cannot use library functions.
To give you the context : I want to create child processes which run the following function. Each float value is sent by the parent through the pipe and is read by one of the children processes which is supposed to sleep in order to let another child process read 1 other value and sleep. When a process wakes up, he's supposed to check if it can get a value from the pipe to sleep again, otherwise the loop ends and the child process is exited.
void worker(int * pip){
close(pip[1]);
float buffer;
while(read(pip[0], &buffer, sizeof(float)) != 0){
sleep(buffer);
}
exit(1);
}
Each value is written by the parent this way in a loop :
write(pip[1], &values[i], sizeof(float))
c pipe
edited Nov 26 '18 at 10:28
Sourav Ghosh
111k15132191
asked Nov 26 '18 at 10:14
Arthur KlipfelArthur Klipfel
2118
1
Learn about multiplexing system calls such as poll(2)
– Basile Starynkevitch
Nov 26 '18 at 10:17
2
Note that you are likely to go in an infinite loop on read failures (returning -1)
– alamit
Nov 26 '18 at 10:25
add a comment |
I'm trying to read float values through a pipe as long as there is data in it. The problem is that the read function never returns 0 in my case, so my function never gets out of the loop.
Moreover, I cannot use library functions.
To give you the context : I want to create child processes which run the following function. Each float value is sent by the parent through the pipe and is read by one of the children processes which is supposed to sleep in order to let another child process read 1 other value and sleep. When a process wakes up, he's supposed to check if it can get a value from the pipe to sleep again, otherwise the loop ends and the child process is exited.
void worker(int * pip){
close(pip[1]);
float buffer;
while(read(pip[0], &buffer, sizeof(float)) != 0){
sleep(buffer);
}
exit(1);
}
Each value is written by the parent this way in a loop :
write(pip[1], &values[i], sizeof(float))
c pipe
edited Nov 26 '18 at 10:28
Sourav Ghosh
111k15132191
asked Nov 26 '18 at 10:14
Arthur KlipfelArthur Klipfel
2118
I'm trying to read float values through a pipe as long as there is data in it. The problem is that the read function never returns 0 in my case, so my function never gets out of the loop.
Moreover, I cannot use library functions.
To give you the context : I want to create child processes which run the following function. Each float value is sent by the parent through the pipe and is read by one of the children processes which is supposed to sleep in order to let another child process read 1 other value and sleep. When a process wakes up, he's supposed to check if it can get a value from the pipe to sleep again, otherwise the loop ends and the child process is exited.
void worker(int * pip){
close(pip[1]);
float buffer;
while(read(pip[0], &buffer, sizeof(float)) != 0){
sleep(buffer);
}
exit(1);
}
Each value is written by the parent this way in a loop :
write(pip[1], &values[i], sizeof(float))
c pipe
c pipe
edited Nov 26 '18 at 10:28
Sourav Ghosh
111k15132191
asked Nov 26 '18 at 10:14
Arthur KlipfelArthur Klipfel
2118
edited Nov 26 '18 at 10:28
Sourav Ghosh
111k15132191
asked Nov 26 '18 at 10:14
Arthur KlipfelArthur Klipfel
2118
edited Nov 26 '18 at 10:28
Sourav Ghosh
111k15132191
edited Nov 26 '18 at 10:28
Sourav Ghosh
111k15132191
edited Nov 26 '18 at 10:28
Sourav Ghosh
111k15132191
111k15132191
asked Nov 26 '18 at 10:14
Arthur KlipfelArthur Klipfel
2118
asked Nov 26 '18 at 10:14
Arthur KlipfelArthur Klipfel
2118
asked Nov 26 '18 at 10:14
Arthur KlipfelArthur Klipfel
2118
2118
1
Learn about multiplexing system calls such as poll(2)
– Basile Starynkevitch
Nov 26 '18 at 10:17
2
Note that you are likely to go in an infinite loop on read failures (returning -1)
– alamit
Nov 26 '18 at 10:25
add a comment |
1
Learn about multiplexing system calls such as poll(2)
– Basile Starynkevitch
Nov 26 '18 at 10:17
2
Note that you are likely to go in an infinite loop on read failures (returning -1)
– alamit
Nov 26 '18 at 10:25
1
1
Learn about multiplexing system calls such as poll(2)
– Basile Starynkevitch
Nov 26 '18 at 10:17
Learn about multiplexing system calls such as poll(2)
– Basile Starynkevitch
Nov 26 '18 at 10:17
2
2
Note that you are likely to go in an infinite loop on read failures (returning -1)
– alamit
Nov 26 '18 at 10:25
Note that you are likely to go in an infinite loop on read failures (returning -1)
– alamit
Nov 26 '18 at 10:25
add a comment |
1 Answer
1
active
oldest
votes
You should call close(pip[1]); after parent write all data.
The following code could work:
#include <sys/types.h>
#include <sys/wait.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
void worker(int * pip){
close(pip[1]);
float buffer;
while(read(pip[0], &buffer, sizeof(float)) != 0){
printf("%fn", buffer);
}
exit(1);
}
int main() {
int pip[2];
pipe(pip);
if (fork() == 0) {
worker(pip);
exit(1);
}
close(pip[0]);
float a[4] = {1.1, 2.2, 3.3, 4.4};
for (int i = 0; i != sizeof(a) / sizeof(a[0]); ++i)
write(pip[1], a + i, sizeof(a[0]));
close(pip[1]);
wait(NULL);
return 0;
}
answered Nov 26 '18 at 10:37
Yunbin LiuYunbin Liu
1,2762515
add a comment |
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1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
You should call close(pip[1]); after parent write all data.
The following code could work:
#include <sys/types.h>
#include <sys/wait.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
void worker(int * pip){
close(pip[1]);
float buffer;
while(read(pip[0], &buffer, sizeof(float)) != 0){
printf("%fn", buffer);
}
exit(1);
}
int main() {
int pip[2];
pipe(pip);
if (fork() == 0) {
worker(pip);
exit(1);
}
close(pip[0]);
float a[4] = {1.1, 2.2, 3.3, 4.4};
for (int i = 0; i != sizeof(a) / sizeof(a[0]); ++i)
write(pip[1], a + i, sizeof(a[0]));
close(pip[1]);
wait(NULL);
return 0;
}
answered Nov 26 '18 at 10:37
Yunbin LiuYunbin Liu
1,2762515
add a comment |
You should call close(pip[1]); after parent write all data.
The following code could work:
#include <sys/types.h>
#include <sys/wait.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
void worker(int * pip){
close(pip[1]);
float buffer;
while(read(pip[0], &buffer, sizeof(float)) != 0){
printf("%fn", buffer);
}
exit(1);
}
int main() {
int pip[2];
pipe(pip);
if (fork() == 0) {
worker(pip);
exit(1);
}
close(pip[0]);
float a[4] = {1.1, 2.2, 3.3, 4.4};
for (int i = 0; i != sizeof(a) / sizeof(a[0]); ++i)
write(pip[1], a + i, sizeof(a[0]));
close(pip[1]);
wait(NULL);
return 0;
}
answered Nov 26 '18 at 10:37
Yunbin LiuYunbin Liu
1,2762515
add a comment |
You should call close(pip[1]); after parent write all data.
The following code could work:
#include <sys/types.h>
#include <sys/wait.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
void worker(int * pip){
close(pip[1]);
float buffer;
while(read(pip[0], &buffer, sizeof(float)) != 0){
printf("%fn", buffer);
}
exit(1);
}
int main() {
int pip[2];
pipe(pip);
if (fork() == 0) {
worker(pip);
exit(1);
}
close(pip[0]);
float a[4] = {1.1, 2.2, 3.3, 4.4};
for (int i = 0; i != sizeof(a) / sizeof(a[0]); ++i)
write(pip[1], a + i, sizeof(a[0]));
close(pip[1]);
wait(NULL);
return 0;
}
answered Nov 26 '18 at 10:37
Yunbin LiuYunbin Liu
1,2762515
You should call close(pip[1]); after parent write all data.
The following code could work:
#include <sys/types.h>
#include <sys/wait.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
void worker(int * pip){
close(pip[1]);
float buffer;
while(read(pip[0], &buffer, sizeof(float)) != 0){
printf("%fn", buffer);
}
exit(1);
}
int main() {
int pip[2];
pipe(pip);
if (fork() == 0) {
worker(pip);
exit(1);
}
close(pip[0]);
float a[4] = {1.1, 2.2, 3.3, 4.4};
for (int i = 0; i != sizeof(a) / sizeof(a[0]); ++i)
write(pip[1], a + i, sizeof(a[0]));
close(pip[1]);
wait(NULL);
return 0;
}
answered Nov 26 '18 at 10:37
Yunbin LiuYunbin Liu
1,2762515
answered Nov 26 '18 at 10:37
Yunbin LiuYunbin Liu
1,2762515
answered Nov 26 '18 at 10:37
Yunbin LiuYunbin Liu
1,2762515
answered Nov 26 '18 at 10:37
Yunbin LiuYunbin Liu
1,2762515
1,2762515
add a comment |
add a comment |
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1
Learn about multiplexing system calls such as poll(2)
– Basile Starynkevitch
Nov 26 '18 at 10:17
2
Note that you are likely to go in an infinite loop on read failures (returning -1)
– alamit
Nov 26 '18 at 10:25