please help! adding to strings

[coni]

I am trying to write to files called something that I give in my command-line. For example I call "a.out blahblah.c16", and then I want to create two new strings "blahblah.o" and "blahblah.syms" and then write to them. I've tried strcat, and doing it character by character, but nothing seems to work.

This is what I'm working with so far:

	char * name = malloc(sizeof(strlen(argv[1])));
	strncpy(name, argv[1], s1);
	printf("name is '%s'\n", name);
        char o[MAXWORDLEN]; //max is 20
	char syms[MAXWORDLEN];

	puto(o, name);
	putsyms(syms, name);
	printf("o is '%s'\n", o);
	printf("syms is '%s'\n", syms);

	input = fopen(argv[1], "r");
	output = fopen(syms, "w");
	output2 = fopen(o, "w");

here are the methods

int puto(char *str, char *name) {
	int i = 0;
	char c = *name;
	char * name2 = name;
	while ( ((c>=48 && c <=122) || c == 46) && c!='\0') {
		str[i] = c;
		name++;
		c = *name;
		i++;
	}
	str[i++] = '.';
	str[i++] = 'o';
	str[i] = '\0';
	name = name2;
	return 0;
}

int putsyms(char *str, char *name) {
	int i = 0;
	char c = *name;
		while (c != '\0') {
			str[i] = c;
			name++;
			c = *name;
			i++;
		}
		str[i++] = '.';
		str[i++] = 's';
		str[i++] = 'y';
		str[i++] = 'm';
		str[i++] = 's';
		str[i] = '\0';
		return 0;
}

>a.out llo.small.int.c16
name is 'llo.small.int'
o is ''
syms is 'llo.small.int.syms'
FINISHED
HEX IS 8302
Segmentation fault (core dumped)

when I run it in eclipse, it writes to the files fine, but now I'm using a linux server and that doesn't work. Thanks in advance.

[Sebastiani]

>> strlen(argv[1])

Good start there, except you forgot to account for the null terminator.

>> sizeof(strlen(argv[1]))

strlen returns an int, and sizeof(int) isn't what you want.

>> strncpy(name, argv[1], s1);

Not sure what 's1' is, but a better approach would be to store the amount that you passed to malloc somewhere and usee that value instead. Also, not applicable here, but just keep in mind that strncpy doesn't guarantee a null terminator. You might create a wrapper function to make sure that gets done...

Just a suggestion:

int puto(char *str, char *name) {
    int i = 0;
    char c;
    while ((c = name[i]) != '\0' && (c>=48 && c <=122)) {
        str[i++] = c;
    }
    str[i++] = '.';
    str[i++] = 'o';
    str[i] = '\0';
    return 0;
}

Also, it would be a better practice to pass a maximum length to the functions to prevent possible overflows.