*: add most of the required setup_common_bufsiz() calls
[oweals/busybox.git] / findutils / xargs.c
index a6f8058fc2997dcdad8a55b6be8432e4bfdfa416..ae01a49beaf8cb151ddece900e50df613d22bb84 100644 (file)
 /*
  * Mini xargs implementation for busybox
  *
- * Copyright (C) 2000 by Lineo, inc.
- * Written by Erik Andersen <andersen@lineo.com>, <andersee@debian.org>
+ * (C) 2002,2003 by Vladimir Oleynik <dzo@simtreas.ru>
  *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
+ * Special thanks
+ * - Mark Whitley and Glenn McGrath for stimulus to rewrite :)
+ * - Mike Rendell <michael@cs.mun.ca>
+ * and David MacKenzie <djm@gnu.ai.mit.edu>.
  *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- * General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ * Licensed under GPLv2 or later, see file LICENSE in this source tree.
  *
+ * xargs is described in the Single Unix Specification v3 at
+ * http://www.opengroup.org/onlinepubs/007904975/utilities/xargs.html
  */
 
-#include "internal.h"
-#include <stdlib.h>
-#include <stdio.h>
-#include <string.h>
-#include <errno.h>
-#include <getopt.h>
+//config:config XARGS
+//config:      bool "xargs"
+//config:      default y
+//config:      help
+//config:        xargs is used to execute a specified command for
+//config:        every item from standard input.
+//config:
+//config:config FEATURE_XARGS_SUPPORT_CONFIRMATION
+//config:      bool "Enable -p: prompt and confirmation"
+//config:      default y
+//config:      depends on XARGS
+//config:      help
+//config:        Support -p: prompt the user whether to run each command
+//config:        line and read a line from the terminal.
+//config:
+//config:config FEATURE_XARGS_SUPPORT_QUOTES
+//config:      bool "Enable single and double quotes and backslash"
+//config:      default y
+//config:      depends on XARGS
+//config:      help
+//config:        Support quoting in the input.
+//config:
+//config:config FEATURE_XARGS_SUPPORT_TERMOPT
+//config:      bool "Enable -x: exit if -s or -n is exceeded"
+//config:      default y
+//config:      depends on XARGS
+//config:      help
+//config:        Support -x: exit if the command size (see the -s or -n option)
+//config:        is exceeded.
+//config:
+//config:config FEATURE_XARGS_SUPPORT_ZERO_TERM
+//config:      bool "Enable -0: NUL-terminated input"
+//config:      default y
+//config:      depends on XARGS
+//config:      help
+//config:        Support -0: input items are terminated by a NUL character
+//config:        instead of whitespace, and the quotes and backslash
+//config:        are not special.
+//config:
+//config:config FEATURE_XARGS_SUPPORT_REPL_STR
+//config:      bool "Enable -I STR: string to replace"
+//config:      default y
+//config:      depends on XARGS
+//config:      help
+//config:        Support -I STR and -i[STR] options.
 
+//applet:IF_XARGS(APPLET_NOEXEC(xargs, xargs, BB_DIR_USR_BIN, BB_SUID_DROP, xargs))
 
-int xargs_main(int argc, char **argv)
+//kbuild:lib-$(CONFIG_XARGS) += xargs.o
+
+#include "libbb.h"
+#include "common_bufsiz.h"
+
+/* This is a NOEXEC applet. Be very careful! */
+
+
+//#define dbg_msg(...) bb_error_msg(__VA_ARGS__)
+#define dbg_msg(...) ((void)0)
+
+
+#ifdef TEST
+# ifndef ENABLE_FEATURE_XARGS_SUPPORT_CONFIRMATION
+#  define ENABLE_FEATURE_XARGS_SUPPORT_CONFIRMATION 1
+# endif
+# ifndef ENABLE_FEATURE_XARGS_SUPPORT_QUOTES
+#  define ENABLE_FEATURE_XARGS_SUPPORT_QUOTES 1
+# endif
+# ifndef ENABLE_FEATURE_XARGS_SUPPORT_TERMOPT
+#  define ENABLE_FEATURE_XARGS_SUPPORT_TERMOPT 1
+# endif
+# ifndef ENABLE_FEATURE_XARGS_SUPPORT_ZERO_TERM
+#  define ENABLE_FEATURE_XARGS_SUPPORT_ZERO_TERM 1
+# endif
+#endif
+
+
+struct globals {
+       char **args;
+#if ENABLE_FEATURE_XARGS_SUPPORT_REPL_STR
+       char **argv;
+       const char *repl_str;
+       char eol_ch;
+#endif
+       const char *eof_str;
+       int idx;
+} FIX_ALIASING;
+#define G (*(struct globals*)bb_common_bufsiz1)
+#define INIT_G() do { \
+       setup_common_bufsiz(); \
+       G.eof_str = NULL; /* need to clear by hand because we are NOEXEC applet */ \
+       IF_FEATURE_XARGS_SUPPORT_REPL_STR(G.repl_str = "{}";) \
+       IF_FEATURE_XARGS_SUPPORT_REPL_STR(G.eol_ch = '\n';) \
+} while (0)
+
+
+static int xargs_exec(void)
 {
-       char *in_from_stdin = NULL;
-       char *args_from_cmdline = NULL;
-       char *cmd_to_be_executed = NULL;
-       char traceflag = 0;
-       int len_args_from_cmdline, len_cmd_to_be_executed, len, opt;
-
-       /* Note that we do not use getopt here, since
-        * we only want to interpret initial options,
-        * not options passed to commands */
-       while (--argc && **(++argv) == '-') {
-               while (*++(*argv)) {
-                       switch (**argv) {
-                               case 't':
-                                       traceflag=1;
-                                       break;
-                               default:
-                                       fatalError(xargs_usage);
+       int status;
+
+       status = spawn_and_wait(G.args);
+       if (status < 0) {
+               bb_simple_perror_msg(G.args[0]);
+               return errno == ENOENT ? 127 : 126;
+       }
+       if (status == 255) {
+               bb_error_msg("%s: exited with status 255; aborting", G.args[0]);
+               return 124;
+       }
+       if (status >= 0x180) {
+               bb_error_msg("'%s' terminated by signal %d",
+                       G.args[0], status - 0x180);
+               return 125;
+       }
+       if (status)
+               return 123;
+       return 0;
+}
+
+/* In POSIX/C locale isspace is only these chars: "\t\n\v\f\r" and space.
+ * "\t\n\v\f\r" happen to have ASCII codes 9,10,11,12,13.
+ */
+#define ISSPACE(a) ({ unsigned char xargs__isspace = (a) - 9; xargs__isspace == (' ' - 9) || xargs__isspace <= (13 - 9); })
+
+static void store_param(char *s)
+{
+       /* Grow by 256 elements at once */
+       if (!(G.idx & 0xff)) { /* G.idx == N*256 */
+               /* Enlarge, make G.args[(N+1)*256 - 1] last valid idx */
+               G.args = xrealloc(G.args, sizeof(G.args[0]) * (G.idx + 0x100));
+       }
+       G.args[G.idx++] = s;
+}
+
+/* process[0]_stdin:
+ * Read characters into buf[n_max_chars+1], and when parameter delimiter
+ * is seen, store the address of a new parameter to args[].
+ * If reading discovers that last chars do not form the complete
+ * parameter, the pointer to the first such "tail character" is returned.
+ * (buf has extra byte at the end to accommodate terminating NUL
+ * of "tail characters" string).
+ * Otherwise, the returned pointer points to NUL byte.
+ * On entry, buf[] may contain some "seed chars" which are to become
+ * the beginning of the first parameter.
+ */
+
+#if ENABLE_FEATURE_XARGS_SUPPORT_QUOTES
+static char* FAST_FUNC process_stdin(int n_max_chars, int n_max_arg, char *buf)
+{
+#define NORM      0
+#define QUOTE     1
+#define BACKSLASH 2
+#define SPACE     4
+       char q = '\0';             /* quote char */
+       char state = NORM;
+       char *s = buf;             /* start of the word */
+       char *p = s + strlen(buf); /* end of the word */
+
+       buf += n_max_chars;        /* past buffer's end */
+
+       /* "goto ret" is used instead of "break" to make control flow
+        * more obvious: */
+
+       while (1) {
+               int c = getchar();
+               if (c == EOF) {
+                       if (p != s)
+                               goto close_word;
+                       goto ret;
+               }
+               if (state == BACKSLASH) {
+                       state = NORM;
+                       goto set;
+               }
+               if (state == QUOTE) {
+                       if (c != q)
+                               goto set;
+                       q = '\0';
+                       state = NORM;
+               } else { /* if (state == NORM) */
+                       if (ISSPACE(c)) {
+                               if (p != s) {
+ close_word:
+                                       state = SPACE;
+                                       c = '\0';
+                                       goto set;
+                               }
+                       } else {
+                               if (c == '\\') {
+                                       state = BACKSLASH;
+                               } else if (c == '\'' || c == '"') {
+                                       q = c;
+                                       state = QUOTE;
+                               } else {
+ set:
+                                       *p++ = c;
+                               }
+                       }
+               }
+               if (state == SPACE) {   /* word's delimiter or EOF detected */
+                       if (q) {
+                               bb_error_msg_and_die("unmatched %s quote",
+                                       q == '\'' ? "single" : "double");
+                       }
+                       /* A full word is loaded */
+                       if (G.eof_str) {
+                               if (strcmp(s, G.eof_str) == 0) {
+                                       while (getchar() != EOF)
+                                               continue;
+                                       p = s;
+                                       goto ret;
                                }
+                       }
+                       store_param(s);
+                       dbg_msg("args[]:'%s'", s);
+                       s = p;
+                       n_max_arg--;
+                       if (n_max_arg == 0) {
+                               goto ret;
+                       }
+                       state = NORM;
+               }
+               if (p == buf) {
+                       goto ret;
                }
        }
+ ret:
+       *p = '\0';
+       /* store_param(NULL) - caller will do it */
+       dbg_msg("return:'%s'", s);
+       return s;
+}
+#else
+/* The variant does not support single quotes, double quotes or backslash */
+static char* FAST_FUNC process_stdin(int n_max_chars, int n_max_arg, char *buf)
+{
+       char *s = buf;             /* start of the word */
+       char *p = s + strlen(buf); /* end of the word */
 
-       /* Store the command and arguments to be executed (from the command line) */
-       if (argc == 1) {
-               len_args_from_cmdline = 6;
-               args_from_cmdline = xmalloc(len_args_from_cmdline);
-               strcat(args_from_cmdline, "echo ");
-       } else {
-               opt=strlen(*argv);
-               len_args_from_cmdline = (opt > 10)? opt : 10;
-               args_from_cmdline = xcalloc(len_args_from_cmdline, sizeof(char));
-               while (argc-- > 0) {
-                       if (strlen(*argv) + strlen(args_from_cmdline) >
-                               len_args_from_cmdline) {
-                               len_args_from_cmdline += strlen(*argv);
-                               args_from_cmdline =
-                                       xrealloc(args_from_cmdline,
-                                                        len_args_from_cmdline+1);
+       buf += n_max_chars;        /* past buffer's end */
+
+       while (1) {
+               int c = getchar();
+               if (c == EOF) {
+                       if (p == s)
+                               goto ret;
+               }
+               if (c == EOF || ISSPACE(c)) {
+                       if (p == s)
+                               continue;
+                       c = EOF;
+               }
+               *p++ = (c == EOF ? '\0' : c);
+               if (c == EOF) { /* word's delimiter or EOF detected */
+                       /* A full word is loaded */
+                       if (G.eof_str) {
+                               if (strcmp(s, G.eof_str) == 0) {
+                                       while (getchar() != EOF)
+                                               continue;
+                                       p = s;
+                                       goto ret;
+                               }
                        }
-                       strcat(args_from_cmdline, *argv);
-                       strcat(args_from_cmdline, " ");
+                       store_param(s);
+                       dbg_msg("args[]:'%s'", s);
+                       s = p;
+                       n_max_arg--;
+                       if (n_max_arg == 0) {
+                               goto ret;
+                       }
+               }
+               if (p == buf) {
+                       goto ret;
                }
        }
+ ret:
+       *p = '\0';
+       /* store_param(NULL) - caller will do it */
+       dbg_msg("return:'%s'", s);
+       return s;
+}
+#endif /* FEATURE_XARGS_SUPPORT_QUOTES */
 
-       /* Set up some space for the command to be executed to be held in */
-       len_cmd_to_be_executed=10;
-       cmd_to_be_executed = xcalloc(len_cmd_to_be_executed, sizeof(char));
-       strcpy(cmd_to_be_executed, args_from_cmdline);
-       strcat(cmd_to_be_executed, " ");
+#if ENABLE_FEATURE_XARGS_SUPPORT_ZERO_TERM
+static char* FAST_FUNC process0_stdin(int n_max_chars, int n_max_arg, char *buf)
+{
+       char *s = buf;             /* start of the word */
+       char *p = s + strlen(buf); /* end of the word */
 
-       /* Now, read in one line at a time from stdin, and run command+args on it */
-       in_from_stdin = get_line_from_file(stdin);
-       for (;in_from_stdin!=NULL;) {
-               char *tmp;
-               len = strlen(in_from_stdin) + len_args_from_cmdline;
-               len_cmd_to_be_executed+=len+3;
-               cmd_to_be_executed=xrealloc(cmd_to_be_executed, len_cmd_to_be_executed);
+       buf += n_max_chars;        /* past buffer's end */
 
-               /* Strip out any \n's, so we just get one command to run */
-               while( (tmp = strchr(in_from_stdin, '\n')) != NULL )
-                       *tmp=' ';
+       while (1) {
+               int c = getchar();
+               if (c == EOF) {
+                       if (p == s)
+                               goto ret;
+                       c = '\0';
+               }
+               *p++ = c;
+               if (c == '\0') {   /* NUL or EOF detected */
+                       /* A full word is loaded */
+                       store_param(s);
+                       dbg_msg("args[]:'%s'", s);
+                       s = p;
+                       n_max_arg--;
+                       if (n_max_arg == 0) {
+                               goto ret;
+                       }
+               }
+               if (p == buf) {
+                       goto ret;
+               }
+       }
+ ret:
+       *p = '\0';
+       /* store_param(NULL) - caller will do it */
+       dbg_msg("return:'%s'", s);
+       return s;
+}
+#endif /* FEATURE_XARGS_SUPPORT_ZERO_TERM */
 
-               strcat(cmd_to_be_executed, in_from_stdin);
-               strcat(cmd_to_be_executed, " ");
-       
-               free(in_from_stdin);
-               in_from_stdin = get_line_from_file(stdin);
+#if ENABLE_FEATURE_XARGS_SUPPORT_REPL_STR
+/*
+ * Used if -I<repl> was specified.
+ * In this mode, words aren't appended to PROG ARGS.
+ * Instead, entire input line is read, then <repl> string
+ * in every PROG and ARG is replaced with the line:
+ *  echo -e "ho ho\nhi" | xargs -I_ cmd __ _
+ * results in "cmd 'ho hoho ho' 'ho ho'"; "cmd 'hihi' 'hi'".
+ * -n MAX_ARGS seems to be ignored.
+ * Tested with GNU findutils 4.5.10.
+ */
+//FIXME: n_max_chars is not handled the same way as in GNU findutils.
+//FIXME: quoting is not implemented.
+static char* FAST_FUNC process_stdin_with_replace(int n_max_chars, int n_max_arg UNUSED_PARAM, char *buf)
+{
+       int i;
+       char *end, *p;
+
+       /* Free strings from last invocation, if any */
+       for (i = 0; G.args && G.args[i]; i++)
+               if (G.args[i] != G.argv[i])
+                       free(G.args[i]);
+
+       end = buf + n_max_chars;
+       p = buf;
+
+       while (1) {
+               int c = getchar();
+               if (c == EOF || c == G.eol_ch) {
+                       if (p == buf)
+                               goto ret; /* empty line */
+                       c = '\0';
+               }
+               *p++ = c;
+               if (c == '\0') {   /* EOL or EOF detected */
+                       i = 0;
+                       while (G.argv[i]) {
+                               char *arg = G.argv[i];
+                               int count = count_strstr(arg, G.repl_str);
+                               if (count != 0)
+                                       arg = xmalloc_substitute_string(arg, count, G.repl_str, buf);
+                               store_param(arg);
+                               dbg_msg("args[]:'%s'", arg);
+                               i++;
+                       }
+                       p = buf;
+                       goto ret;
+               }
+               if (p == end) {
+                       goto ret;
+               }
        }
+ ret:
+       *p = '\0';
+       /* store_param(NULL) - caller will do it */
+       dbg_msg("return:'%s'", buf);
+       return buf;
+}
+#endif
+
+#if ENABLE_FEATURE_XARGS_SUPPORT_CONFIRMATION
+/* Prompt the user for a response, and
+ * if user responds affirmatively, return true;
+ * otherwise, return false. Uses "/dev/tty", not stdin.
+ */
+static int xargs_ask_confirmation(void)
+{
+       FILE *tty_stream;
+       int c, savec;
 
-       if (traceflag==1)
-               fputs(cmd_to_be_executed, stderr);
+       tty_stream = xfopen_for_read(CURRENT_TTY);
+       fputs(" ?...", stderr);
+       fflush_all();
+       c = savec = getc(tty_stream);
+       while (c != EOF && c != '\n')
+               c = getc(tty_stream);
+       fclose(tty_stream);
+       return (savec == 'y' || savec == 'Y');
+}
+#else
+# define xargs_ask_confirmation() 1
+#endif
 
-       if ((system(cmd_to_be_executed) != 0) && (errno != 0))
-               fatalError("%s", strerror(errno));
+//usage:#define xargs_trivial_usage
+//usage:       "[OPTIONS] [PROG ARGS]"
+//usage:#define xargs_full_usage "\n\n"
+//usage:       "Run PROG on every item given by stdin\n"
+//usage:       IF_FEATURE_XARGS_SUPPORT_CONFIRMATION(
+//usage:     "\n       -p      Ask user whether to run each command"
+//usage:       )
+//usage:     "\n       -r      Don't run command if input is empty"
+//usage:       IF_FEATURE_XARGS_SUPPORT_ZERO_TERM(
+//usage:     "\n       -0      Input is separated by NUL characters"
+//usage:       )
+//usage:     "\n       -t      Print the command on stderr before execution"
+//usage:     "\n       -e[STR] STR stops input processing"
+//usage:     "\n       -n N    Pass no more than N args to PROG"
+//usage:     "\n       -s N    Pass command line of no more than N bytes"
+//usage:       IF_FEATURE_XARGS_SUPPORT_REPL_STR(
+//usage:     "\n       -I STR  Replace STR within PROG ARGS with input line"
+//usage:       )
+//usage:       IF_FEATURE_XARGS_SUPPORT_TERMOPT(
+//usage:     "\n       -x      Exit if size is exceeded"
+//usage:       )
+//usage:#define xargs_example_usage
+//usage:       "$ ls | xargs gzip\n"
+//usage:       "$ find . -name '*.c' -print | xargs rm\n"
 
+/* Correct regardless of combination of CONFIG_xxx */
+enum {
+       OPTBIT_VERBOSE = 0,
+       OPTBIT_NO_EMPTY,
+       OPTBIT_UPTO_NUMBER,
+       OPTBIT_UPTO_SIZE,
+       OPTBIT_EOF_STRING,
+       OPTBIT_EOF_STRING1,
+       IF_FEATURE_XARGS_SUPPORT_CONFIRMATION(OPTBIT_INTERACTIVE,)
+       IF_FEATURE_XARGS_SUPPORT_TERMOPT(     OPTBIT_TERMINATE  ,)
+       IF_FEATURE_XARGS_SUPPORT_ZERO_TERM(   OPTBIT_ZEROTERM   ,)
+       IF_FEATURE_XARGS_SUPPORT_REPL_STR(    OPTBIT_REPLSTR    ,)
+       IF_FEATURE_XARGS_SUPPORT_REPL_STR(    OPTBIT_REPLSTR1   ,)
 
-#ifdef BB_FEATURE_CLEAN_UP
-       free(args_from_cmdline);
-       free(cmd_to_be_executed);
+       OPT_VERBOSE     = 1 << OPTBIT_VERBOSE    ,
+       OPT_NO_EMPTY    = 1 << OPTBIT_NO_EMPTY   ,
+       OPT_UPTO_NUMBER = 1 << OPTBIT_UPTO_NUMBER,
+       OPT_UPTO_SIZE   = 1 << OPTBIT_UPTO_SIZE  ,
+       OPT_EOF_STRING  = 1 << OPTBIT_EOF_STRING , /* GNU: -e[<param>] */
+       OPT_EOF_STRING1 = 1 << OPTBIT_EOF_STRING1, /* SUS: -E<param> */
+       OPT_INTERACTIVE = IF_FEATURE_XARGS_SUPPORT_CONFIRMATION((1 << OPTBIT_INTERACTIVE)) + 0,
+       OPT_TERMINATE   = IF_FEATURE_XARGS_SUPPORT_TERMOPT(     (1 << OPTBIT_TERMINATE  )) + 0,
+       OPT_ZEROTERM    = IF_FEATURE_XARGS_SUPPORT_ZERO_TERM(   (1 << OPTBIT_ZEROTERM   )) + 0,
+       OPT_REPLSTR     = IF_FEATURE_XARGS_SUPPORT_REPL_STR(    (1 << OPTBIT_REPLSTR    )) + 0,
+       OPT_REPLSTR1    = IF_FEATURE_XARGS_SUPPORT_REPL_STR(    (1 << OPTBIT_REPLSTR1   )) + 0,
+};
+#define OPTION_STR "+trn:s:e::E:" \
+       IF_FEATURE_XARGS_SUPPORT_CONFIRMATION("p") \
+       IF_FEATURE_XARGS_SUPPORT_TERMOPT(     "x") \
+       IF_FEATURE_XARGS_SUPPORT_ZERO_TERM(   "0") \
+       IF_FEATURE_XARGS_SUPPORT_REPL_STR(    "I:i::")
+
+int xargs_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
+int xargs_main(int argc, char **argv)
+{
+       int i;
+       int child_error = 0;
+       char *max_args;
+       char *max_chars;
+       char *buf;
+       unsigned opt;
+       int n_max_chars;
+       int n_max_arg;
+#if ENABLE_FEATURE_XARGS_SUPPORT_ZERO_TERM \
+ || ENABLE_FEATURE_XARGS_SUPPORT_REPL_STR
+       char* FAST_FUNC (*read_args)(int, int, char*) = process_stdin;
+#else
+#define read_args process_stdin
 #endif
 
-       return 0;
+       INIT_G();
+
+#if ENABLE_DESKTOP && ENABLE_LONG_OPTS
+       /* For example, Fedora's build system uses --no-run-if-empty */
+       applet_long_options =
+               "no-run-if-empty\0" No_argument "r"
+               ;
+#endif
+       opt = getopt32(argv, OPTION_STR,
+               &max_args, &max_chars, &G.eof_str, &G.eof_str
+               IF_FEATURE_XARGS_SUPPORT_REPL_STR(, &G.repl_str, &G.repl_str)
+       );
+
+       /* -E ""? You may wonder why not just omit -E?
+        * This is used for portability:
+        * old xargs was using "_" as default for -E / -e */
+       if ((opt & OPT_EOF_STRING1) && G.eof_str[0] == '\0')
+               G.eof_str = NULL;
+
+       if (opt & OPT_ZEROTERM) {
+               IF_FEATURE_XARGS_SUPPORT_ZERO_TERM(read_args = process0_stdin;)
+               IF_FEATURE_XARGS_SUPPORT_REPL_STR(G.eol_ch = '\0';)
+       }
+
+       argv += optind;
+       argc -= optind;
+       if (!argv[0]) {
+               /* default behavior is to echo all the filenames */
+               *--argv = (char*)"echo";
+               argc++;
+       }
+
+       /*
+        * The Open Group Base Specifications Issue 6:
+        * "The xargs utility shall limit the command line length such that
+        * when the command line is invoked, the combined argument
+        * and environment lists (see the exec family of functions
+        * in the System Interfaces volume of IEEE Std 1003.1-2001)
+        * shall not exceed {ARG_MAX}-2048 bytes".
+        */
+       n_max_chars = bb_arg_max();
+       if (n_max_chars > 32 * 1024)
+               n_max_chars = 32 * 1024;
+       /*
+        * POSIX suggests substracting 2048 bytes from sysconf(_SC_ARG_MAX)
+        * so that the process may safely modify its environment.
+        */
+       n_max_chars -= 2048;
+
+       if (opt & OPT_UPTO_SIZE) {
+               n_max_chars = xatou_range(max_chars, 1, INT_MAX);
+       }
+       /* Account for prepended fixed arguments */
+       {
+               size_t n_chars = 0;
+               for (i = 0; argv[i]; i++) {
+                       n_chars += strlen(argv[i]) + 1;
+               }
+               n_max_chars -= n_chars;
+       }
+       /* Sanity check */
+       if (n_max_chars <= 0) {
+               bb_error_msg_and_die("can't fit single argument within argument list size limit");
+       }
+
+       buf = xzalloc(n_max_chars + 1);
+
+       n_max_arg = n_max_chars;
+       if (opt & OPT_UPTO_NUMBER) {
+               n_max_arg = xatou_range(max_args, 1, INT_MAX);
+               /* Not necessary, we use growable args[]: */
+               /* if (n_max_arg > n_max_chars) n_max_arg = n_max_chars */
+       }
+
+#if ENABLE_FEATURE_XARGS_SUPPORT_REPL_STR
+       if (opt & (OPT_REPLSTR | OPT_REPLSTR1)) {
+               /*
+                * -I<str>:
+                * Unmodified args are kept in G.argv[i],
+                * G.args[i] receives malloced G.argv[i] with <str> replaced
+                * with input line. Setting this up:
+                */
+               G.args = NULL;
+               G.argv = argv;
+               argc = 0;
+               read_args = process_stdin_with_replace;
+               /* Make -I imply -r. GNU findutils seems to do the same: */
+               /* (otherwise "echo -n | xargs -I% echo %" would SEGV) */
+               opt |= OPT_NO_EMPTY;
+       } else
+#endif
+       {
+               /* Allocate pointers for execvp.
+                * We can statically allocate (argc + n_max_arg + 1) elements
+                * and do not bother with resizing args[], but on 64-bit machines
+                * this results in args[] vector which is ~8 times bigger
+                * than n_max_chars! That is, with n_max_chars == 20k,
+                * args[] will take 160k (!), which will most likely be
+                * almost entirely unused.
+                *
+                * See store_param() for matching 256-step growth logic
+                */
+               G.args = xmalloc(sizeof(G.args[0]) * ((argc + 0xff) & ~0xff));
+               /* Store the command to be executed, part 1 */
+               for (i = 0; argv[i]; i++)
+                       G.args[i] = argv[i];
+       }
+
+       while (1) {
+               char *rem;
+
+               G.idx = argc;
+               rem = read_args(n_max_chars, n_max_arg, buf);
+               store_param(NULL);
+
+               if (!G.args[argc]) {
+                       if (*rem != '\0')
+                               bb_error_msg_and_die("argument line too long");
+                       if (opt & OPT_NO_EMPTY)
+                               break;
+               }
+               opt |= OPT_NO_EMPTY;
+
+               if (opt & (OPT_INTERACTIVE | OPT_VERBOSE)) {
+                       const char *fmt = " %s" + 1;
+                       char **args = G.args;
+                       for (i = 0; args[i]; i++) {
+                               fprintf(stderr, fmt, args[i]);
+                               fmt = " %s";
+                       }
+                       if (!(opt & OPT_INTERACTIVE))
+                               bb_putchar_stderr('\n');
+               }
+
+               if (!(opt & OPT_INTERACTIVE) || xargs_ask_confirmation()) {
+                       child_error = xargs_exec();
+               }
+
+               if (child_error > 0 && child_error != 123) {
+                       break;
+               }
+
+               overlapping_strcpy(buf, rem);
+       } /* while */
+
+       if (ENABLE_FEATURE_CLEAN_UP) {
+               free(G.args);
+               free(buf);
+       }
+
+       return child_error;
 }
-/*
-Local Variables:
-c-file-style: "linux"
-c-basic-offset: 4
-tab-width: 4
-End:
-*/
 
+
+#ifdef TEST
+
+const char *applet_name = "debug stuff usage";
+
+void bb_show_usage(void)
+{
+       fprintf(stderr, "Usage: %s [-p] [-r] [-t] -[x] [-n max_arg] [-s max_chars]\n",
+               applet_name);
+       exit(EXIT_FAILURE);
+}
+
+int main(int argc, char **argv)
+{
+       return xargs_main(argc, argv);
+}
+#endif /* TEST */