a version of `strings(1)` that isn’t dependent on a linker

0strings.md

strings

a version of strings(1) that isn’t dependent on a linker. Dumps all strings of any given file.

Based off code provided by toybox

Makefile

TARGET := strings

SRC    := src/strings.c

all: $(TARGET)

$(TARGET): $(SRC)
	$(CC) $(LDFLAGS) $^ -o $@

clean:
	$(RM) $(TARGET)

strings.c

// from https://github.com/landley/toybox/blob/master/toys/posix/strings.c

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>

#define BUFSIZE 4096

long n = 4;
char buf[BUFSIZE];

void do_strings(char *filename) {
    int fd = open(filename, O_RDONLY);
    if (fd < 0) {
        perror(filename);
        exit(EXIT_FAILURE);
    }

    int nread, i, wlen = n, count = 0;
    off_t offset = 0;
    char *string = 0;

    string = calloc(wlen+1, sizeof(char));
    if (!string) {
        perror("calloc");
        exit(EXIT_FAILURE);
    }

    for (i = nread = 0; ;i++) {
        if (i >= nread) {
            nread = read(fd, buf, sizeof(buf));
            i = 0;
            if (nread < 0) {
                perror(filename);
                exit(EXIT_FAILURE);
            }
            if (nread < 1) {
                if (count) goto flush;
                break;
            }
        }

        offset++;
        if ((buf[i]>=32 && buf[i]<=126) || buf[i]=='\t') {
            if (count == wlen) fputc(buf[i], stdout);
            else {
                string[count++] = buf[i];
                if (count == wlen) {
                    printf("%s", string);
                }
            }
            continue;
        }
flush:
        if (count == wlen) putchar('\n');
        count = 0;
    }
    close(fd);
    free(string);
}

int main(int argc, char *argv[]) {
    if (argc < 2) {
        fprintf(stderr, "Usage: %s [file ...]\n", argv[0]);
        exit(EXIT_FAILURE);
    }

    for (int i = 1; i < argc; i++) {
        do_strings(argv[i]);
    }

    return 0;
}