open() call path error - c

Question

I am having issues with the input of open If my first argument is a path I get this output:
Error en open: No such file or directory
but if its file name there is no error, how can in fix it? The code is as follows:
#include<sys/types.h> //Primitive system data types for abstraction of implementation-dependent data types.
//POSIX Standard: 2.6 Primitive System Data Types <sys/types.h>
#include<sys/stat.h>
#include<fcntl.h>
#include<stdlib.h>
#include<stdio.h>
#include<errno.h>
char buf1[]="abcdefghij";
char buf2[]="ABCDEFGHIJ";
int main(int argc, char *argv[])
{
int fd;
if( (fd=open(argv[1],O_CREAT|O_TRUNC|O_WRONLY,S_IRUSR|S_IWUSR))<0) {
printf("\nError %d en open",errno);
perror("\nError en open");
exit(-1);
}
if(write(fd,buf1,10) != 10) {
perror("\nError en primer write");
exit(-1);
}
if(lseek(fd,40,SEEK_SET) < 0) {
perror("\nError en lseek");
exit(-1);
}
if(write(fd,buf2,10) != 10) {
perror("\nError en segundo write");
exit(-1);
}
return 0;
}
The test sequence is:
root#ubuntu:/home/pablo/...# ./tarea1 /home/pablo/hello > temp ; cat temp
root#ubuntu:/home/pablo/...# ./tarea1 /home/pablo/>hello ; cat hello
Error en open: Is a directory

Answer 1

Your second test sequence is:
# ./tarea1 /home/pablo/>hello
This would be more clearly written as:
# ./tarea1 /home/pablo/ >hello
The shell gives your program the name of a directory, /home/pablo/, and creates a file hello in the current directory. Any standard output from your program goes to the file. When your program tries to open the directory for writing, it fails — not even root is allowed to write in a directory. (You can open a directory for reading, but can't actually read from it; that's useful for the various *at() functions (such as openat()), but not otherwise.)
If you really want a > in your file name, enclose the whole name in quotes:
# ./tarea1 "/home/pablo/>hello"
However, you don't really want a > in your file name; it just makes life difficult (not quite as bad as a newline in the file name, but close).

Answer 2

You haven't said whether you're using Linux or not. But I'm going to guess you are.
Linux open has this really annoying feature that for some reason the file doesn't already exist and you use the version of open that doesn't have the third mode parameter, it fails to create the file. At least that's what I've found. If however the file does exist and has the appropriate permissions, the 2 parameter open call should succeed.
The fix is to change the open call to:
fd=open(argv[1],O_CREAT|O_TRUNC|O_WRONLY,S_IRUSR|S_IWUSR, S_IRWXU)
By the way, I hope you're aware that the program will pass null to the open call if there are no parameters.