bore

commit cb98d9607e45ec1cd3469a731bc4dc3f9f5ad01a
parent bed094ca7c1be13351cfe65479311c4f7ba0c6c2
Author: aabacchus <ben@bvnf.space>
Date:   Thu, 16 Sep 2021 02:45:50 +0100

cat: add

Diffstat:
M
Makefile
 | 
2
+-
A
cat.c
 | 
58
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

2 files changed, 59 insertions(+), 1 deletion(-)
diff --git a/Makefile b/Makefile
@@ -1,6 +1,6 @@
 .POSIX:
 
-BINS =
+BINS = cat
 XCFLAGS = $(CFLAGS) -Wall -Wextra -Wpedantic -g
 
 .PHONY: clean
diff --git a/cat.c b/cat.c
@@ -0,0 +1,58 @@
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+#define BUF_SIZE 4096
+
+int
+cat(int fd, char *fname) {
+    unsigned char buf[BUF_SIZE];
+    ssize_t n;
+    while ((n = read(fd, buf, BUF_SIZE)) > 0) {
+        if (n == -1){
+            fprintf(stderr, "cat: read %s: %s\n", fname, strerror(errno));
+            return 1;
+        }
+        if (write(1, buf, n) == -1) {
+            fprintf(stderr, "cat: write: %s\n", strerror(errno));
+            return 1;
+        }
+    }
+    return 0;
+}
+
+int
+main(int argc, char **argv) {
+    if (argc == 1)
+        return cat(0, "stdin");
+
+    int fd;
+    int err = 0;
+    char *fname;
+
+    while (*++argv) {
+        if (**argv == '-') {
+            fd = 0;
+            fname = "stdin";
+        } else {
+            fd = open(*argv, O_RDONLY);
+            if (fd == -1) {
+                fprintf(stderr, "cat: open %s: %s\n", *argv, strerror(errno));
+                err = 1;
+                continue;
+            }
+            fname = *argv;
+        }
+        if (cat(fd, fname) != 0) {
+            err = 1;
+            continue;
+        }
+        if (close(fd) == -1){
+            fprintf(stderr, "cat: close %s: %s\n", fname, strerror(errno));
+            err = 1;
+        }
+    }
+    return err;
+}