Final (I think) version of xargs. Throw away all that tedious string

scrubbing, and quit using system.  Instead, use fork() and exec(), which
yields and smaller, simpler, and cleaner design.
 -Erik

1 files changed, 62 insertions, 94 deletions

diff --git a/xargs.c b/xargs.c
index 21bfb6bbe..b8ac31aa0 100644
--- a/xargs.c
+++ b/xargs.c
@@ -28,68 +28,19 @@
 #include <errno.h>
 #include <getopt.h>
 #include <ctype.h>
-
-/* get_sh_safe_line_from_file() - This function reads an entire line from a text file
- * up to a newline. It returns a malloc'ed char * which must be stored and
- * free'ed  by the caller. */
-extern char *get_sh_safe_line_from_file(FILE *file)
-{
-	static const int GROWBY = 80; /* how large we will grow strings by */
-
-	char ch, last_ch = 0;
-	char tmp[]=" ";
-	int idx = 0;
-	char *linebuf = NULL;
-	int linebufsz = 0;
-
-	while (1) {
-		ch = fgetc(file);
-		if (ch == EOF)
-			break;
-		
-		/* grow the line buffer as necessary */
-		while (idx > linebufsz-4)
-			linebuf = xrealloc(linebuf, linebufsz += GROWBY);
-
-		/* Remove any extra spaces */
-		if (last_ch == ' ' && ch == ' ')
-			continue;
-
-		/* Replace any tabs with spaces */
-		if (ch == '\t')
-			ch=' ';
-
-		/* Escape any characters that are treated specially by /bin/sh */
-		*tmp=ch;
-		if (strpbrk(tmp, "\\~`!$^&*()=|{}[];\"'<>?#") != NULL && last_ch!='\\') {
-			linebuf[idx++] = '\\';
-		}
-
-		linebuf[idx++] = ch;
-		last_ch=ch;
-
-		if (ch == '\n')
-			break;
-	}
-	if (idx == 0 && last_ch!=0)
-		linebuf[idx++]=' ';
-
-	if (idx == 0)
-		return NULL;
-
-	linebuf[idx] = 0;
-	return linebuf;
-}
-
+#include <sys/types.h>
+#include <sys/wait.h>
 
 
 int xargs_main(int argc, char **argv)
 {
 	char *in_from_stdin = NULL;
-	char *args_from_cmdline = NULL;
+	char *args = NULL;
 	char *cmd_to_be_executed = NULL;
 	char traceflag = 0;
-	int len_args_from_cmdline, len_cmd_to_be_executed, len, opt;
+	int len_args=10, len_cmd_to_be_executed, opt;
+	pid_t pid;
+	int wpid, status;
 
 	/* Note that we do not use getopt here, since
 	 * we only want to interpret initial options,
@@ -102,50 +53,45 @@ int xargs_main(int argc, char **argv)
 					break;
 				default:
 					fatalError(xargs_usage);
-				}
+			}
 		}
 	}
 
-	/* Store the command and arguments to be executed (from the command line) */
+	/* Store the command to be executed (taken from the command line) */
 	if (argc == 0) {
-		len_args_from_cmdline = 6;
-		args_from_cmdline = xmalloc(len_args_from_cmdline);
-		strcat(args_from_cmdline, "echo ");
+		len_cmd_to_be_executed=6;
+		cmd_to_be_executed = xmalloc(len_cmd_to_be_executed);
+		strcat(cmd_to_be_executed, "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);
-			}
-			strcat(args_from_cmdline, *argv);
-			strcat(args_from_cmdline, " ");
-			++argv;
-		}
+		len_cmd_to_be_executed = (opt > 10)? opt : 10;
+		cmd_to_be_executed = xcalloc(len_cmd_to_be_executed, sizeof(char));
+		strcat(cmd_to_be_executed, *argv);
 	}
 
-	/* 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);
 
-	/* Now, read in one line at a time from stdin, and run command+args on it */
-	in_from_stdin = get_sh_safe_line_from_file(stdin);
+	/* Now, read in one line at a time from stdin, and stroe this to be used later 
+	 * as an argument to the command we just stored */
+	in_from_stdin = get_line_from_file(stdin);
 	for (;in_from_stdin!=NULL;) {
 		char *tmp;
 		opt = strlen(in_from_stdin);
-		len = opt + 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);
+		len_args += opt + 3;
+		args=xrealloc(args, len_args);
 
 		/* Strip out the final \n */
 		in_from_stdin[opt-1]=' ';
-			
+
+		/* Replace any tabs with spaces */
+		while( (tmp = strchr(in_from_stdin, '\t')) != NULL )
+			*tmp=' ';
+
+		/* Strip out any extra intra-word spaces */
+		while( (tmp = strstr(in_from_stdin, "  ")) != NULL ) {
+			opt = strlen(in_from_stdin);
+			memmove(tmp, tmp+1, opt-(tmp-in_from_stdin));
+		}
+
 		/* trim trailing whitespace */
 		opt = strlen(in_from_stdin) - 1;
 		while (isspace(in_from_stdin[opt]))
@@ -157,26 +103,49 @@ int xargs_main(int argc, char **argv)
 		while(isspace(*tmp))
 			tmp++;
 
-		strcat(cmd_to_be_executed, tmp);
-		strcat(cmd_to_be_executed, " ");
-	
+		strcat(args, tmp);
+		strcat(args, " ");
+
 		free(in_from_stdin);
-		in_from_stdin = get_sh_safe_line_from_file(stdin);
+		in_from_stdin = get_line_from_file(stdin);
 	}
 
-	if (traceflag==1)
+	if (traceflag==1) {
 		fputs(cmd_to_be_executed, stderr);
+		fputs(args, stderr);
+	}
 
-	if ((system(cmd_to_be_executed) != 0) && (errno != 0))
-		fatalError("%s", strerror(errno));
+	if ((pid = fork()) == 0) {
+		char *cmd[255];
+		int i=1;
+
+		//printf("argv[0]='%s'\n", cmd_to_be_executed);
+		cmd[0] = cmd_to_be_executed;
+		while (--argc && ++argv && *argv ) {
+			//printf("argv[%d]='%s'\n", i, *argv);
+			cmd[i++]=*argv;
+		}
+		//printf("argv[%d]='%s'\n", i, args);
+		cmd[i++] = args;
+		cmd[i] = NULL;
+		execvp(cmd_to_be_executed, cmd);
+
+		/* What?  Still here?  Exit with an error */
+		fatalError("%s: %s\n", cmd_to_be_executed, strerror(errno));
+	}
+	/* Wait for a child process to exit */
+	wpid = wait(&status);
 
 
 #ifdef BB_FEATURE_CLEAN_UP
-	free(args_from_cmdline);
+	free(args);
 	free(cmd_to_be_executed);
 #endif
 
-	return 0;
+	if (wpid > 0)
+		return (WEXITSTATUS(status));
+	else 
+		return EXIT_FAILURE;
 }
 /*
 Local Variables:
@@ -185,4 +154,3 @@ c-basic-offset: 4
 tab-width: 4
 End:
 */
-