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#include <stdio.h>
#include <unistd.h>
/* 20251104 bkw: implement the simple checksum used by ALF.
Dumbest possible algo: all the bytes are added together and
the bottom 16 bits of the result is the checksum. */
char *self;
void alfsum(const char *file, FILE *f) {
int c;
unsigned long sum = 0;
while((c = fgetc(f)) != EOF)
sum += c;
printf("%8s\t%04x\n", file, (unsigned int)(sum & 0xffff));
}
int main(int argc, char **argv) {
int errs = 0;
char *file;
FILE *f;
self = argv[0];
/* if the first arg is a - followed by anything at all, assume --help */
if(argc < 2 || (argc == 2 && argv[1][0] == '-' && argv[1][1])) {
fprintf(stderr,
"usage: %s filename [filename ...]\n"
"\t(use - to read from standard input)\n",
self);
return -1;
}
while((file = *++argv)) {
if(argv[0][0] == '-' && !argv[0][1]) {
if(isatty(0))
fprintf(stderr, "%s: reading from stdin...\n", self);
f = stdin;
file = " (stdin)";
} else if(!(f = fopen(file, "rb"))) {
fprintf(stderr, "%s: ", self);
perror(file);
errs++;
continue;
}
alfsum(file, f);
fclose(f);
}
return errs > 254 ? 254 : errs;
}
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