Re: Redirection issue


Barry Margolin wrote:
In article <1156959022.965599.76790@xxxxxxxxxxxxxxxxxxxxxxxxxxx>,
"souissipro" <souissipro@xxxxxxxx> wrote:

int
redir_cmd(char *argv[],char *in, char *out)

You don't seem to handle the case where only on direction is being
redirected. Perhaps you should allow a null point to be passed for the
ones that aren't being redirected, and check for this below before
calling open() and dup2().

This would also allow you to avoid having separate simple_cmd() and
redir_cmd() functions -- a simple command is just what you get if both
in and out are null, because it won't redirect anything.

{
int i;
int pid, status;
int fd1, fd2;
int dummy;

if (strcmp(argv[0],"exit")==0)
return do_exit(argv);
for(i=0;argv[i]!=NULL;i++)
printf("argv[%i]=\"%s\";\n",i,argv[i]);

if (strcmp(argv[0],"cd")==0)
{
return chdir(*argv);
}

if (fork() == 0) {
fd1 = open(in, O_RDONLY);
if (fd1 < 0) {
perror("can't open file : in");
exit(1);
}

if (dup2(fd1, out) != 0) {

This should be:

if (dup2(fd1, STDIN_FILENO) != 0) {

perror("catf1f2: dup2(in, 0)");
exit(1);
}
close(fd1);

fd2 = open(out, O_WRONLY | O_TRUNC | O_CREAT, 0644);
if (fd2 < 0) {
perror("catinout: out");
exit(2);
}
/*
if (dup2(fd2, 1) != 1) {

It's preferable to use STDOUT_FILENO instead of hard-coding 1.

perror("catf1f2: dup2(out, 1)");
exit(1);
}
*/
close(fd2);

execvp(*argv, argv);
perror(*argv);
exit(1);

}

/*
* parent executes wait.
*/
else {
wait(&dummy);
}

}

--
Barry Margolin, barmar@xxxxxxxxxxxx
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***
*** PLEASE don't copy me on replies, I'll read them in the group ***


Hi Barry ,

Thanks for your comments.

I have changed the fd1 and fd2 types and also 0 and 1 by STDOUT_FILENO
and STDIN_FILENO. The redirection is now working. The shell compiles .
The commands of the input file (input.txt) have been executed and the
output is sent to the outout file (ouput.txt).
Now, I have another issues in the sens that the simple command and the
commands passed in a file are not executed.
In the main function I have treated 3 cases : simple command, input
file, and redirection. But the problem may be in the rediretion
(redirect_cmd) function and as you said the code is not handle the case
where only on direction is being
redirected.
Could you please clarify this by some lines of codes in this fucntion.


Thanks,

Souissipro

.

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