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#include <stdio.h>
#include <ctype.h>
#include <string.h>
/* The C Programming Language: 2nd Edition
*
* Exercise 7-1: Write a program that converts upper case to lower or lower
* case to upper, depending on the name it is invoked with, as found in
* `argv[0]`.
*
* Notes: This one is, strangely, very easy. The primary gotcha is in the
* argv[0] check. The simplest solution I came up with was to check argv[0]
* for *both* upper and lower. If for some reason they're both in the path,
* the one that occurred later in the string takes precedence, since it's
* most likely to be the name of the executable itself rather than the
* directory containing the binary.
*
* Edge cases, gotta love'em.
*/
int main(int argc, char *argv[]) {
char c;
int lpos, upos;
char *plow, *pupp;
while ((c = getchar()) != EOF) {
plow = strstr(argv[0], "lower");
pupp = strstr(argv[0], "upper");
if (plow != NULL) {
lpos = (int)(plow - argv[0]);
} else {
lpos = -1;
}
if (pupp != NULL) {
upos = (int)(pupp - argv[0]);
} else {
upos = -1;
}
if (isalpha(c)) {
/* These two are only equal when neither are found in argv[0].
* The odds of this happening are slim, but still possible.
*/
if (lpos > upos) {
c = tolower(c);
}
if (upos > lpos) {
c = toupper(c);
}
}
putchar(c);
}
return 0;
}
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