Implement head

1 files changed, 62 insertions, 0 deletions

diff --git a/toys/head.c b/toys/head.c
new file mode 100644
index 00000000..8f0baa24
--- /dev/null
+++ b/toys/head.c
@@ -0,0 +1,62 @@
+/* vi: set sw=4 ts=4:
+ *
+ * head.c - copy first lines from input to stdout.
+ *
+ * Copyright 2006 Timothy Elliott <tle@holymonkey.com>
+ *
+ * See http://www.opengroup.org/onlinepubs/009695399/utilities/head.html
+
+USE_HEAD(NEWTOY(head, "n#", TOYFLAG_BIN))
+
+config HEAD
+	bool "head"
+	default y
+	help
+	  usage: head [-n number] [file...]
+	  Copy first lines from files to stdout. If no files listed, copy from
+	  stdin. Filename "-" is a synonym for stdin.
+
+	  -n	Number of lines to copy.
+*/
+
+#include "toys.h"
+
+DEFINE_GLOBALS(
+	long lines;
+	int file_no;
+)
+
+#define TT this.head
+
+static void do_head(int fd, char *name)
+{
+	int i, len, lines=TT.lines, size=sizeof(toybuf);
+
+	if (toys.optc > 1) {
+		// Print an extra newline for all but the first file
+		if (TT.file_no++ > 0) printf("\n");
+		printf("==> %s <==\n", name);
+	}
+
+	for (;lines>0;) {
+		len = read(fd, toybuf, size);
+		if (len<0) {
+			perror_msg("%s",name);
+			toys.exitval = EXIT_FAILURE;
+		}
+		if (len<1) break;
+		
+		for(i=0; i<len; i++) {
+			if (toybuf[i] == '\n' && --lines < 1) break;
+		}
+		xwrite(1, toybuf, i+1);
+	}
+}
+
+void head_main(void)
+{
+	if (!toys.optflags) TT.lines = 10;
+	if (TT.lines < 0) perror_exit("Invalid number of lines.");
+	TT.file_no = 0;
+	loopfiles(toys.optargs, do_head);
+}