unistd.h is a C/C++ header files contains needed to provide access to the POSIX operating systems
Links:
https://en.wikipedia.org/wiki/Unistd.h
https://pubs.opengroup.org/onlinepubs/009695399/basedefs/unistd.h.html
Questions tagged [unistd.h]
175 questions
0
votes
2 answers
Compile file from inside the application with execl
I'm trying to compile a file from my application,with this action:
- (IBAction)build:(id)sender
{
pid_t pid=fork();
int status;
if(!pid)
{
execl("/Developer/usr/bin/gcc","-o main ~/main.c");
exit(0);
}
…
Ramy Al Zuhouri
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0
votes
1 answer
Porting klib's knetfile.c|h to windows, when I sub in the "windows unistd.h", I get error C2036: 'void *' : unknown size
First, by "windows unistd.h", I mean the example located here: "is there a replacement for unistd.h for windows?
I am attempting to massage knetfile.c so that it can be compiled for windows64. My first step was to remove the unistd.h include,…
rlong
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0
votes
1 answer
Using grep in execl with file descriptor
I'm trying to do the following:
execl("/bin/grep","grep","print",fd,NULL);
where fd is a file descriptor.
So basically this should grep for "print" in the file pointed to by fd.
It doesn't seem to work although I get no compile errors/warnings.
It…
ffledgling
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-1
votes
1 answer
How to use write() and read() in unistd.h
I'm trying to use the functions read() and write() from unistd.h, but whenever I try input anything, it does not work. And I am only alowed to use functions from fcntl.h and unistd.h, not those from stdio.h.
Here is my code:
#include …
Gabi
- 9
- 4
-1
votes
1 answer
System call read result display random characters after the result
I've recieved this assignment where I have to read from a file.txt(max size 4096B) four times, basically splitting it in 4 strings of equal size. I have to fill this structure(just consider field 'msg', i think the problem is there):
struct message…
iLux24
- 3
- 1
-1
votes
1 answer
Whats wrong with rand function in C
what can be the reason of bad result in generating random number in C? See my code below. The result should be number between 0 - 1. But when i print random number the result is: Doba prichodu: 690522220 n-times. And yes i am using…
Peter Kulas
- 21
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-1
votes
3 answers
What does fork() == 0 returns?
I have 2 programs and I'm very confused on the return of fork() in child process
The first program would call fork() and assign it to p. When p == 0, it implies child process.
// The first program
p = fork();
if (p == 0)
{
// child…
Peter
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-1
votes
1 answer
How can I visualise how many processes this code creates?
How many processes does this piece of code create?
for(int i = 0 ; i < 5 ; i++){
if(fork() == fork())
break;
}
tugayicoru
- 39
- 3
-1
votes
2 answers
atof coredump with getopt
I'm writing a C++ application which converts fahrenheit to celsius and kelvin, and kelvin to celsius and fahrenheit, etc. Since it's stupid to write an interative application here, I decided to familiarize myself with the getopt function in…
Distant Graphics
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-1
votes
2 answers
Why does my code exit with exit code: 0 even though the loop condition is still valid?
I am trying to use fork with execvp to run two shell commands concurrently. I have two problems which are when I input mkdir folder1&mkdir folder2, it creates a folder named folder1 and another folder named folder2? (the question mark is included in…
Ambitions
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-1
votes
2 answers
Libraries "X11/Xlib.h", "X11/Xutil.h", "unistd.h" for Windows
I've done a C program that takes the RGB values (0-255) of a pixel of the screen knowing its position (x,y). It works in Linux, but when I try to compile it in Visual Studio (Windows), crashes because libraries X11/Xlib.h, X11/Xutil.h, unistd.h…
Sergio
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-1
votes
1 answer
unistd : no such file or directory
I have the following test.cpp file :
#include
int main()
{
return 0;
}
I just want to compile this but I still have the following :
$ g++ test.cpp
test.cpp:1:18: fatal error: unistd: No such file or directory
#include
…
vmonteco
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-1
votes
1 answer
Why isn't execlp() printing output to the terminal?
I am trying to link the output of a child process into the input of a parent process; the parent process is to execute a system call or command using the child's output.
I have looked to the following threads for answer; however, I didn't quite get…
Tyler K
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-1
votes
2 answers
How to know what number a system call has in linux
So I need to know what number a certain system call has , it says that I can check which number a systemcall has in unistd.h file but how/where can I find that file?
Antivirus
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-1
votes
1 answer
How can i keep reading from a file using read from unistd.h
I'm using Qt for a project. I'll constanly read from a file with read from unistd.h, but how can i do that? I have tried to use an infinite while loop but my application crash when i do that.
PS i'm beginner when it comes to Qt and fileoperation…
Loc Dai Le
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