CODEWITHSUNDEEP
ccommand-line-arguments
Nicolas Huet
Nicolas Huet

Reputation: 3

Bug with ' * ' as argument

I'm a beginner and try to learn some c. I make a program to learn the pointer on functions in with I give 3 arguments to the program at launch: an int, an operator and another int. Everything works fine with %, -, +, and /. But for * I have a very weird bug. After a lot of write() everywhere to find where it starts to bug, I find that it is at the very beginning: when I display argv[2][0], it display the good char for everything exept for the * where it shows "Makefile"... I really don't understand this issue and I don't find anything related to * and arguments bugs. I don't even bug on the pointers or other thing since it's from the start.

Here is the start of the code so you can see:

#include"header.h"

void    ft_putchar(char c)
{
    write(1, &c, 1);
}

void    ft_putstr(char *str)
{
    int i;

    i = 0;
    while (str[i] != '\0')
    {
        ft_putchar(str[i]);
        i++;
    }
}

int main(int argc, char **argv)
{
    int a;
    int b;
    char    operator;

    ft_putchar(argv[2]); //here it shows "Makefile"...

And some output: ( first the char representation, then the number of chars, then another time the char representation but further away in the code and then the result, * is always 0 because it just quit the main after not following any conditions next)

➜  exercice05 ./ft_op 100 / 5
/1/20
➜  exercice05 ./ft_op 100 + 5
+1+105
➜  exercice05 ./ft_op 100 - 5
-1-95
➜  exercice05 ./ft_op 100 % 5
%1%0
➜  exercice05 ./ft_op 100 * 5
Makefile80

The bug is so strange I can only imagine it's something obvious but I'm clueless right now to find it. I do have a Makefile in my dir but I really don't see where would be the problem. I'm on macOS Catalina, tried on bash and zsh, same result. Just in case here is the makefile :

TARGET = ft_op
SRC = $(wildcard *.c)
OBJ = $(SRC:.c =.o)
FLAG = -Wall -Wextra -Werror
CC = gcc

$(TARGET): $(OBJ)
    $(CC) $(FLAG) $^  -o $@

.PHONY: clean fclean

clean:
    rm -f *.o
fclean: clean
    rm -f $(TARGET)

Thank you

Upvotes: 0

Views: 59

Answers (1)

Joseph Sible-Reinstate Monica
Joseph Sible-Reinstate Monica

Reputation: 48672

Your C program isn't getting * as an argument, because your shell is expanding it first. You need to use it as '*' or \* when you call your program: exercice05 ./ft_op 100 '*' 5 or exercice05 ./ft_op 100 \* 5

Compare the outputs of echo *, echo '*' and echo \* to make it more clear.

Upvotes: 1

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