Please find below the code and the output which I am getting.
My C code is in c:/turboc3/bin directory
and my output macid.txt is in c:/turboc3/disk.
Here is the code which I am compiling
#include <stdio.h>
#include <conio.h>
#include <string.h>
int main ()
{
//char mac[200];
FILE *fp;
clrscr();
// fp=fopen("c:\macid.txt","w");
system("GETMAC>c:/macid.txt");
fp=fopen("c:/macid.txt","r");
if(fp!=NULL)
{
char line[128];
while(fgets(line,sizeof line,fp)!=NULL)
{
char *nwln=strchr(line,'\n');
char *ptr;
if(nwln!=NULL)
*nwln='\0';
ptr=strstr(line,"Physical Address");
if(ptr!=NULL)
{
printf("%s\n",ptr);
break;
}
}
}
getch();
return 0;
}
The output is:
Illegal command: GETMAC.
Can anyone guide me through this?
Illegal command: GETMAC implies, that it tries to run it but can't.
First, things to fix : Remember to escape \ inside string. Do not use / as path separator.
Then, Things to try, in approximate order: Try with full path to GETMAC. Try without redirection. Try with different program. Wrap GETMAC into bat file, which does the redirection.
I am not sure how your file macid.txt resides in c:/turboc3/disk, but - I think you can solve this problem by giving a full path to the system() function call.
LIke this:
system("c:/windows/system32/getmac.exe > macid.txt");
Related
I'm trying my luck with C lately and I came across to this question where I'm stuck.
I've a hello.c file
CODE 1
#include<stdio.h>
#include<stdlib.h>
int main(){
printf("Hello World");
return 0;
}
I open this file and display the content using the following C program (CODE 2)
CODE 2
#include<fcntl.h>
#include<stdio.h>
int main() {
FILE *fd;
char ch;
fd = fopen("/home/hello.c","r");
if( fd != NULL ) {
while((ch = getc( fd )) != EOF){
putchar(ch);
}
}
return 0;
}
However, I want the output of this code to be Hello World, i.e output of the hello.c file which is read.
How can that be done?
In order to run a c file, first you need to compile it into machine code then execute it.
To compile it: run gcc source-file -o executable-file
To run, execute: executable-file
In order to to the same things in C, use system() function from <stdlib.h>
const char* tempFile = "./tempfile";
const char* sourceFile = "hello.c";
const char compileCommand[255];
sprintf(compileCommand, "gcc %s -o %s", sourceFile, tempFile);
system(compileCommand);
system(tempFile);
This code hasn't been tested.
Currently, in the second program, you are reading hello.c file. So the output of CODE2 will be the contents of hello.c. i.e. #include<stdio.h>...
For what you need, in CODE1, you need to write the output of the program into a separate file (say a.txt) and then read a.txt in CODE2.
Hope this is a sufficient hint for you to solve further.
Your "CODE 2" would have to invoke a C-compiler to compile "CODE 1" and then run it using system() or a function provided by your operating system.
BTW: It is either int main(void) or int main(int argc, char** argv), NOT int main().
As general solution, you may try also to have a look to a C interpreter, like Cling, and try to include it in your project.
How do I get the absolute path to the directory of the currently executing command in C? I'm looking for something similar to the command dirname "$(readlink -f "$0")" in a shell script. For instance, if the C binary is /home/august/foo/bar and it's executed as foo/bar I want to get the result /home/august/foo.
Maybe try POSIX realpath() with argv[0]; something like the following (works on my machine):
#include <limits.h> /* PATH_MAX */
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char **argv) {
char buf[PATH_MAX];
char *res = realpath(argv[0], buf);
(void)argc; /* make compiler happy */
if (res) {
printf("Binary is at %s.\n", buf);
} else {
perror("realpath");
exit(EXIT_FAILURE);
}
return 0;
}
One alternative to argv[0] and realpath(3) on Linux is to use /proc/self/exe, which is a symbolic link pointing to the executable. You can use readlink(2) to get the pathname from it. See proc(5) for more information.
argv[0] is allowed to be NULL by the way (though this usually wouldn't happen in practice). It is also not guaranteed to contain the path used to run the command, though it will when starting programs from the shell.
I have come to the conclusion that there is no portable way for a commpiled executable to get the path to its directory. The obvious alternative is to pass an environment variable to the executable telling it where it is located.
My C code which runs on Ubuntu has line
system("ls -l | wc > temp.txt");
I want to make it work on windows so that It has to be OS Independent.How can I do that.
Can any one help me?
I would guess that the particular code shown is probably going to get the first value from the "temp.txt" file at some point and use it as a count of files (actually number of files plus one)
Instead of that you could use C code like this
#include <stdio.h>
#include <sys/types.h>
#include <dirent.h>
int main() {
DIR *cwd;
int c=1; /* like +1 */
struct dirent *d;
if ((cwd=opendir(".")) ) {
while((d=readdir(cwd))) {
if (*(d->d_name) != '.') c++; /* ignore dot files */
}
} else {
perror("opendir fail");
return(1);
}
printf("the first number in temp.txt would be %d", c);
return(0);
}
Whatever the system() call result is doing, this is my answer: rewrite it in C, which you have working on both systems
I wrote little program to print "Hello world" in C. I'm not a C programmer, but I liked to try it. In my program there is an error. Please tell me what is it?
This is my program:
int main(){
printf("Hello World");
}
I wrote this with my Java Experiences. I can't find what is wrong.
You can't directly use printf() function as in Java. You should tell the compiler that you are going to use the input/output stream. You can tell it in this line:
#include <stdio.h>
and also you should enter this line at the end of the source code:
return 0;
this will tell the compiler :
"If the program succeed It will return 0 otherwise It will return any other number"
This means if your program is successful main() function will return 0. Then the compile know the program is Ok.
Then at last your complete code is:
#include <stdio.h>
int main() {
printf("Hello world");
return 0;
}
To compile this and see the word "Hello World", just save this file as a .c file and Open cmd in your program directory and type
gcc hello.c -o hello && hello
(Replace the 'hello.c' with your filename, and 'hello' with the name you want to put with your .exe file)
Remember My computer is Windows. And this compile code is for windows. If your OS is UNIX like OS. then use this code to compile:
gcc hello.c -o hello
./hello
A full hello world program in C:
#include <stdio.h>
int main(void) {
printf("Hello World\n");
return 0;
}
Then compile (assuming gcc) and execute it:
gcc -o test test.c
./test
First, you have to use a header file.
#include <stdio.h>
What that does is bring up a header file with a bunch of commands in them. That will make it recognize the "printf" piece of code.
Next, you have to close your program. By not having a closing statement, the program will not compile because it doesn't know if that is the end of the code. Use this at the end of your program...
return 0;
That closes the program, meaning that the compiler can stop looking for other code. You may also want to look at some programming manuals (there are dozens of free online ones) to learn about the syntax.
One last thing: Most pieces of C code require a semicolon at the end. This is not true for the "int main" statement, nor is it for the header file which I have defined above. The "return" function that closes the program, does however, need a semicolon.
Hoped this helped.
Should also include a pause at the end:
#include <stdio.h>
int main(void) {
printf("Hello World\n");
//Read a character from the console
getchar();
return 0;
}
Just like import in Java programs, in here you have to include libraries you're using in your program. You have used library function printf, but not included stdio.h.
I agree there are many ways to write one of the simplest way is
#include<stdio.h>
int main(void){
printf("Hello World\n");
return 0;
}
You can even use different ways as suggested above.
You should first look at the structure of "main". Try to understand the various parts as already explained so well in the above answers.
"#include" : The preprocessing directives to be included in the program. But why? Because you are trying to use the functions defined inside them.
int : The return type of "main" program. But why? Because the function calling "main" needs to know if the "main" program has functioned correctly.
main : The entry point of your code. Dont ask why here :-)
main( void ) : To tell the compiler that we are not passing any arguments to program "main"
return 0 : Beacuse you promised "main" that you will return something if "main" will function properly.
Finally the code:
#include <stdio.h>
int main( void )
{
printf( "Hello World\n" ) ; //Notice the '\n' here. Good coding practice.
return 0 ;
}
#include <stdio.h> //Pre-processor commands<br/>
void main() //Starting point of the program<br/>{ //Opening Braces
printf("Hello World\n"); //Print Hello World on the screen<br/>
return 0;
} //Ending Braces
Check it once it will work, I have written it with comments:
#include<stdio.h> //Pre-processor commands
void main() {
printf("Hello World\n"); //Print Hello World on the screen
}
A full hello world program in C:
#include <stdio.h>
int main(void) {
printf("Hello World\n");
return 0;
}
Then compile (assuming gcc) and execute it:
gcc -o test test.c
./test
You can't use printf() function as in Java. You have to tell the compiler what you are going to use.
You can tell this as follows:-
#include <stdio.h>
You must enter this line in last:-
return 0;
Then Your complete code is:-
#include <stdio.h>
int main(){
printf("Hello World");
return 0;
}
For compiling this and see the word "Hello World", just save this file as a .c file and Open cmd in your program directory and type:-
gcc hello.c -o hello && hello
(Replace the 'hello.c' with your filename, and 'hello' with the name you want to put with your .exe file)
Remember My computer is Windows. So I can compile only for Windows OS.
#include <stdio.h>
int main() {
// printf, used to print (display) Hello World
printf("Hello World ! ");
// return 0, as the main function is of type int so it must return an integer value
return 0;
}
Today , When i coding, met a question..my Code as follow:
#include<stdlib.h>
void main()
{
system("dir");
getch();
}
The question : The user Screen is nothing..Why ? where is my result?
If you want the output when using system, at least into something you can read in your application, you need to pipe the output:
system("dir > /tmp/output.txt");
FILE *f = fopen("/tmp/output.txt", "r");
char text[1024]; // max sizeof of 1 kb, any more and I'd consider using `malloc()` instead.
fread(text, 1, 1024, f);
printf("%s\n", text);
fclose(f);
There are some problems in your program, at least one of which has already been mentioned.
void main() should be int main(void).
As I recall, the Windows/DOS getch function is declared in <conio.h>; you should have a #include directive for it. Be aware that both <conio.h> and getch are non-standard.
Since main returns int, you should return an int result.
But none of these problems explain the problem you're seeing.
With these changes:
#include <stdlib.h>
#include <conio.h>
int main(void)
{
system("dir");
getch();
return 0;
}
This should work; it should show a directory listing of whatever directory your program runs in (which is determined by TC; I don't know the details).
It's possible that the program is running in an empty directory, which means the dir command wouldn't show any files, but it should still produce some output.
Try commenting out the system() call and adding a printf call (note the added #include <stdio.h>):
#include <stdio.h>
#include <stdlib.h>
#include <conio.h>
int main(void)
{
printf("Hello, world\n");
getch();
return 0;
}
This should open a console window, print "Hello, world" in it, and wait for you to type Enter.
If you still don't see any output (either no console window, or a console window with nothing in it), then you have a problem that's not related to the system() call. Most likely the problem has to do with the way you're using Turbo C (I presume that's what "TC" stands for).
The main function in every C program is supposed to return an int you are returning void
Change void to int:
#include<stdlib.h>
int main()
{
system("dir");
getch();
}
When I tested, the dir command ran in my console and printed to standard out.
May be he is the running the program directly in the Turbo C IDE and hence his output is not visible. If he runs the program directly from cmd line it works. I remember you need to run Alt - F5 or some other combination to see the output window in Turbo C++