passing integers in place of file descriptor when calling write command in c
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0
down vote
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void main()
{
pid_t pid;
int i;
char buf[BUF_SIZE];
fork();
pid = getpid();
for (i = 1; i <= MAX_COUNT; i++) {
sprintf(buf, "This line is from pid %d, value = %dn", pid, i);
write(1, buf, strlen(buf));
// printf("%s",buf);
}
}
I've got the given simple code to show fork process in c. I noticed that when I pass any value greater than 2 in place of 1 in write command the code does not print anything. Why is this happening?
c
edited Nov 21 at 21:22
NathanOliver
83k15112173
asked Nov 21 at 21:19
Ashray Sinha
51
add a comment |
up vote
0
down vote
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void main()
{
pid_t pid;
int i;
char buf[BUF_SIZE];
fork();
pid = getpid();
for (i = 1; i <= MAX_COUNT; i++) {
sprintf(buf, "This line is from pid %d, value = %dn", pid, i);
write(1, buf, strlen(buf));
// printf("%s",buf);
}
}
I've got the given simple code to show fork process in c. I noticed that when I pass any value greater than 2 in place of 1 in write command the code does not print anything. Why is this happening?
c
edited Nov 21 at 21:22
NathanOliver
83k15112173
asked Nov 21 at 21:19
Ashray Sinha
51
2
You should check thereturnvalue ofwritefor an error.
– Fiddling Bits
Nov 21 at 21:20
1 is for standard output descriptor, 2 is for error. Others aren't open
– Jean-François Fabre
Nov 21 at 21:24
note that theforkpart is irrelevant to the question. The example could be reduced even more to only include awritecall.
– Jean-François Fabre
Nov 21 at 21:31
add a comment |
up vote
0
down vote
favorite
up vote
0
down vote
favorite
void main()
{
pid_t pid;
int i;
char buf[BUF_SIZE];
fork();
pid = getpid();
for (i = 1; i <= MAX_COUNT; i++) {
sprintf(buf, "This line is from pid %d, value = %dn", pid, i);
write(1, buf, strlen(buf));
// printf("%s",buf);
}
}
I've got the given simple code to show fork process in c. I noticed that when I pass any value greater than 2 in place of 1 in write command the code does not print anything. Why is this happening?
c
edited Nov 21 at 21:22
NathanOliver
83k15112173
asked Nov 21 at 21:19
Ashray Sinha
51
void main()
{
pid_t pid;
int i;
char buf[BUF_SIZE];
fork();
pid = getpid();
for (i = 1; i <= MAX_COUNT; i++) {
sprintf(buf, "This line is from pid %d, value = %dn", pid, i);
write(1, buf, strlen(buf));
// printf("%s",buf);
}
}
I've got the given simple code to show fork process in c. I noticed that when I pass any value greater than 2 in place of 1 in write command the code does not print anything. Why is this happening?
c
c
edited Nov 21 at 21:22
NathanOliver
83k15112173
asked Nov 21 at 21:19
Ashray Sinha
51
edited Nov 21 at 21:22
NathanOliver
83k15112173
asked Nov 21 at 21:19
Ashray Sinha
51
edited Nov 21 at 21:22
NathanOliver
83k15112173
edited Nov 21 at 21:22
NathanOliver
83k15112173
edited Nov 21 at 21:22
NathanOliver
83k15112173
83k15112173
asked Nov 21 at 21:19
Ashray Sinha
51
asked Nov 21 at 21:19
Ashray Sinha
51
asked Nov 21 at 21:19
Ashray Sinha
51
51
2
You should check thereturnvalue ofwritefor an error.
– Fiddling Bits
Nov 21 at 21:20
1 is for standard output descriptor, 2 is for error. Others aren't open
– Jean-François Fabre
Nov 21 at 21:24
note that theforkpart is irrelevant to the question. The example could be reduced even more to only include awritecall.
– Jean-François Fabre
Nov 21 at 21:31
add a comment |
2
You should check thereturnvalue ofwritefor an error.
– Fiddling Bits
Nov 21 at 21:20
1 is for standard output descriptor, 2 is for error. Others aren't open
– Jean-François Fabre
Nov 21 at 21:24
note that theforkpart is irrelevant to the question. The example could be reduced even more to only include awritecall.
– Jean-François Fabre
Nov 21 at 21:31
2
2
You should check the
return value of write for an error.– Fiddling Bits
Nov 21 at 21:20
You should check the
return value of write for an error.– Fiddling Bits
Nov 21 at 21:20
1 is for standard output descriptor, 2 is for error. Others aren't open
– Jean-François Fabre
Nov 21 at 21:24
1 is for standard output descriptor, 2 is for error. Others aren't open
– Jean-François Fabre
Nov 21 at 21:24
note that the
fork part is irrelevant to the question. The example could be reduced even more to only include a write call.– Jean-François Fabre
Nov 21 at 21:31
note that the
fork part is irrelevant to the question. The example could be reduced even more to only include a write call.– Jean-François Fabre
Nov 21 at 21:31
add a comment |
1 Answer
1
active
oldest
votes
up vote
1
down vote
accepted
you're performing a raw write call where at the start of your program:
- 1 is the standard output descriptor
- 2 is the standard error descriptor
Both write to the console by default (and 0 is the standard input, cannot be written to)
Other descriptors are invalid unless they've been returned by an open call. Since you don't check the return value of write, you can't see that an error code is returned (probably EBADF, bad file descriptor)
answered Nov 21 at 21:25
Jean-François Fabre
97.9k950107
add a comment |
1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
1
down vote
accepted
you're performing a raw write call where at the start of your program:
- 1 is the standard output descriptor
- 2 is the standard error descriptor
Both write to the console by default (and 0 is the standard input, cannot be written to)
Other descriptors are invalid unless they've been returned by an open call. Since you don't check the return value of write, you can't see that an error code is returned (probably EBADF, bad file descriptor)
answered Nov 21 at 21:25
Jean-François Fabre
97.9k950107
add a comment |
up vote
1
down vote
accepted
you're performing a raw write call where at the start of your program:
- 1 is the standard output descriptor
- 2 is the standard error descriptor
Both write to the console by default (and 0 is the standard input, cannot be written to)
Other descriptors are invalid unless they've been returned by an open call. Since you don't check the return value of write, you can't see that an error code is returned (probably EBADF, bad file descriptor)
answered Nov 21 at 21:25
Jean-François Fabre
97.9k950107
add a comment |
up vote
1
down vote
accepted
up vote
1
down vote
accepted
you're performing a raw write call where at the start of your program:
- 1 is the standard output descriptor
- 2 is the standard error descriptor
Both write to the console by default (and 0 is the standard input, cannot be written to)
Other descriptors are invalid unless they've been returned by an open call. Since you don't check the return value of write, you can't see that an error code is returned (probably EBADF, bad file descriptor)
answered Nov 21 at 21:25
Jean-François Fabre
97.9k950107
you're performing a raw write call where at the start of your program:
- 1 is the standard output descriptor
- 2 is the standard error descriptor
Both write to the console by default (and 0 is the standard input, cannot be written to)
Other descriptors are invalid unless they've been returned by an open call. Since you don't check the return value of write, you can't see that an error code is returned (probably EBADF, bad file descriptor)
answered Nov 21 at 21:25
Jean-François Fabre
97.9k950107
edited Nov 21 at 21:30
answered Nov 21 at 21:25
Jean-François Fabre
97.9k950107
answered Nov 21 at 21:25
Jean-François Fabre
97.9k950107
answered Nov 21 at 21:25
Jean-François Fabre
97.9k950107
97.9k950107
add a comment |
add a comment |
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2
You should check the
returnvalue ofwritefor an error.– Fiddling Bits
Nov 21 at 21:20
1 is for standard output descriptor, 2 is for error. Others aren't open
– Jean-François Fabre
Nov 21 at 21:24
note that the
forkpart is irrelevant to the question. The example could be reduced even more to only include awritecall.– Jean-François Fabre
Nov 21 at 21:31