Added implementations from pdcore

[pdutils] / utils / head / head.c

diff --git a/utils/head/head.c b/utils/head/head.c
new file mode 100644 (file)
index 0000000..bf83ab3
--- /dev/null
+++ b/utils/head/head.c
@@ -0,0 +1,147 @@
+/*
+ * head.c - copy the first part of files
+ *
+ * Version: 2008-1.01
+ * Build:   c89 -o head head.c
+ * Source:  <http://pdcore.sourceforge.net/>
+ * Spec:    <http://www.opengroup.org/onlinepubs/9699919799/utilities/head.html>
+ *
+ * This is free and unencumbered software released into the public domain,
+ * provided "as is", without warranty of any kind, express or implied. See the
+ * file UNLICENSE and the website <http://unlicense.org> for further details.
+ */
+
+
+#define _POSIX_SOURCE
+
+#include <ctype.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <locale.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#define USAGE   "usage: head [-n number] [file ...]\n"
+#define BUFSIZE 4096
+
+static long ctol(char *s);
+static void headfile(int fd, char *fn, int lines);
+static void error(char *s);
+
+static int exitstatus;
+
+
+int main(int argc, char **argv)
+{
+    extern int opterr, optind;
+    extern char *optarg;
+    int c, fd, many, first;
+    char *fn;
+    long lines = 10;
+
+    setlocale(LC_ALL, "");
+    opterr = 0;
+
+    while ((c = getopt(argc, argv, "n:")) != -1)
+        switch (c)
+        {
+        case 'n':
+            if (*optarg && (lines = ctol(optarg)) > 0)
+                break;
+            /* else fall through */
+        default:
+            fprintf(stderr, USAGE);
+            exit(1);
+        }
+
+    if (optind >= argc)
+        headfile(STDIN_FILENO, "stdin", lines);
+    else
+    {
+        many  = (optind + 1 < argc) ? 1 : 0;
+        first = 1;
+
+        while (optind < argc)
+        {
+            fn = argv[optind++];
+
+            if (many)
+            {
+                if (first)
+                    first = 0;
+                else
+                    printf("\n");
+                printf("==> %s <==\n", fn);
+            }
+
+            if (strcmp(fn, "-") == 0)
+                headfile(STDIN_FILENO, "stdin", lines);
+            else
+                if ((fd = open(fn, O_RDONLY)) == -1)
+                    error(fn);
+                else
+                {
+                    headfile(fd, fn, lines);
+                    if (close(fd) == -1)
+                        error(fn);
+                }
+        }
+    }
+
+    return(exitstatus);
+}
+
+
+long ctol(char *s)
+{
+    int badch = 0;
+    char *c = s;
+
+    /* only copes with non-zero, optionally signed, */
+    /* decimal integers; that's all we need         */
+    if (! (isdigit(*c) || *c == '+' || *c == '-'))
+        badch = 1;
+    else
+        for (c++; *c; c++)
+            if (! isdigit(*c))
+                badch = 1;
+
+    return (badch ? 0 : atol(s));
+}
+
+
+void headfile(int fd, char *fn, int lines)
+{
+    unsigned char buf[BUFSIZE], *c;
+    ssize_t n, o;
+
+    while (lines)
+    {
+        if ((n = read(fd, buf, BUFSIZE)) <= 0)
+            break;
+
+        for (c = buf; lines && c < (buf + n); c++)
+            if (*c == '\n')
+                lines--;
+
+        o = lines ? n : c - buf;
+        if (write(STDOUT_FILENO, buf, (size_t)o) != o)
+        {
+            error("stdout");
+            break;
+        }
+    }
+
+    if (n < 0)
+        error(fn);
+}
+
+
+void error(char *s)
+{
+    fprintf(stderr, "head: %s: %s\n", s, strerror(errno));
+    exitstatus = 1;
+}