Add initial version of xargs(1)

Makefile

@@ -93,6 +93,7 @@ SRC = \
 	stat.c     \
 	wc.c       \
 	who.c      \
+	xargs.c    \
 	yes.c
 
 OBJ = $(SRC:.c=.o) $(LIB)

xargs.1

@@ -0,0 +1,28 @@
+.TH XARGS 1 sbase\-VERSION
+.SH NAME
+xargs \- constuct argument list(s) and execute command
+.SH SYNOPSIS
+.B xargs
+.RB [ \-r ]
+.RI [ cmd
+.RI [arg... ] ]
+.SH DESCRIPTION
+xargs reads space, tab, newline and EOF delimited strings from stdin
+and executes the specified cmd with the strings as arguments.
+
+Any arguments specified on the command line are given to the command upon
+each invocation, followed by some number of the arguments read from
+stdin.  The command is repeatedly executed one or more times until stdin
+is exhausted.
+
+Spaces, tabs and newlines may be embedded in arguments using single (`'')
+or double (`"') quotes or backslashes ('\\').  Single quotes escape all
+non-single quote characters, excluding newlines, up to the matching single
+quote.  Double quotes escape all non-double quote characters, excluding
+newlines, up to the matching double quote.  Any single character, including
+newlines, may be escaped by a backslash.
+.SH OPTIONS
+.TP
+.BI \-r
+Do not run the command if there are no arguments.  Normally the command is
+executed at least once even if there are no arguments.

xargs.c

@@ -0,0 +1,241 @@
+/* See LICENSE file for copyright and license details. */
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include "text.h"
+#include "util.h"
+
+enum {
+	NARGS = 5000
+};
+
+static int inputc(void);
+static void deinputc(int);
+static void fillbuf(int);
+static void eatspace(void);
+static int parsequote(int);
+static void parseescape(void);
+static char *poparg(void);
+static void pusharg(char *);
+static int runcmd(void);
+
+static char **cmd;
+static char *argb;
+static size_t argbsz = 1;
+static size_t argbpos;
+static int rflag = 0;
+
+static void
+usage(void)
+{
+	eprintf("usage: %s [-r] [cmd [arg...]]\n", argv0);
+}
+
+int
+main(int argc, char *argv[])
+{
+	long argsz, argmaxsz;
+	char *arg;
+	int i;
+
+	ARGBEGIN {
+	case 'r':
+		rflag = 1;
+		break;
+	default:
+		usage();
+	} ARGEND;
+
+	argmaxsz = sysconf(_SC_ARG_MAX);
+	if (argmaxsz < 0)
+		eprintf("sysconf:");
+	/* Leave some room for environment variables */
+	argmaxsz -= 4 * 1024;
+
+	cmd = malloc(NARGS * sizeof(*cmd));
+	if (!cmd)
+		eprintf("malloc:");
+
+	argb = malloc(argbsz);
+	if (!argb)
+		eprintf("malloc:");
+
+	do {
+		argsz = 0; i = 0;
+		if (argc > 0) {
+			for (; i < argc; i++) {
+				cmd[i] = strdup(argv[i]);
+				argsz += strlen(cmd[i]) + 1;
+			}
+		} else {
+			cmd[i] = strdup("/bin/echo");
+			argsz += strlen(cmd[i]) + 1;
+			i++;
+		}
+		while ((arg = poparg())) {
+			if (argsz + strlen(arg) + 1 > argmaxsz ||
+			    i >= NARGS - 1) {
+				pusharg(arg);
+				break;
+			}
+			cmd[i] = strdup(arg);
+			argsz += strlen(cmd[i]) + 1;
+			i++;
+		}
+		cmd[i] = NULL;
+		if (i == 1 && rflag == 1)
+			;
+		else
+			if (runcmd() == -1)
+				arg = NULL;
+		for (; i >= 0; i--)
+			free(cmd[i]);
+	} while (arg);
+
+	free(argb);
+	free(cmd);
+	return 0;
+}
+
+static int
+inputc(void)
+{
+	int ch;
+
+	ch = getc(stdin);
+	if (ch == EOF && ferror(stdin))
+		eprintf("stdin: read error:");
+	return ch;
+}
+
+static void
+deinputc(int ch)
+{
+	ungetc(ch, stdin);
+}
+
+static void
+fillbuf(int ch)
+{
+	if (argbpos >= argbsz) {
+		argbsz *= 2;
+		argb = realloc(argb, argbsz);
+		if (!argb)
+			eprintf("realloc:");
+	}
+	argb[argbpos] = ch;
+}
+
+static void
+eatspace(void)
+{
+	int ch;
+
+	while ((ch = inputc()) != EOF) {
+		switch (ch) {
+		case ' ': case '\t': case '\n':
+			break;
+		default:
+			deinputc(ch);
+			return;
+		}
+	}
+}
+
+static int
+parsequote(int q)
+{
+	int ch;
+
+	while ((ch = inputc()) != EOF) {
+		if (ch == q) {
+			fillbuf('\0');
+			return 0;
+		}
+		if (ch != '\n') {
+			fillbuf(ch);
+			argbpos++;
+		}
+	}
+	return -1;
+}
+
+static void
+parseescape(void)
+{
+	int ch;
+
+	if ((ch = inputc()) != EOF) {
+		fillbuf(ch);
+		argbpos++;
+	}
+}
+
+static char *
+poparg(void)
+{
+	int ch;
+
+	argbpos = 0;
+	eatspace();
+	while ((ch = inputc()) != EOF) {
+		switch (ch) {
+		case ' ': case '\t': case '\n':
+			fillbuf('\0');
+			deinputc(ch);
+			return argb;
+		case '\'':
+			if (parsequote('\'') == -1)
+				enprintf(EXIT_FAILURE,
+					 "unterminated single quote\n");
+			break;
+		case '\"':
+			if (parsequote('\"') == -1)
+				enprintf(EXIT_FAILURE,
+					 "unterminated double quote\n");
+			break;
+		case '\\':
+			parseescape();
+			break;
+		default:
+			fillbuf(ch);
+			argbpos++;
+			break;
+		}
+	}
+	if (argbpos > 0) {
+		fillbuf('\0');
+		return argb;
+	}
+	return NULL;
+}
+
+static void
+pusharg(char *arg)
+{
+	char *p;
+
+	for (p = &arg[strlen(arg) - 1]; p >= arg; p--)
+		deinputc(*p);
+}
+
+static int
+runcmd(void)
+{
+	pid_t pid;
+	int status;
+
+	pid = fork();
+	if (pid < 0)
+		eprintf("fork:");
+	if (pid == 0) {
+		execvp(*cmd, cmd);
+		eprintf("execvp %s:", *cmd);
+	}
+	wait(&status);
+	if (WIFEXITED(status) && WEXITSTATUS(status) == 255)
+		return -1;
+	return 0;
+}