Add the capability to extract to stdout. Relevant parts from:
https://github.com/mackyle/xar/commit/312a71a77dff76c4bf6ebc8d7a9e64ca1322d8dd 2012-09-15T07:10
https://github.com/mackyle/xar/commit/ba57887b34af69e786b35b34762ab06f17135e2b 2012-09-15T07:29
https://github.com/mackyle/xar/commit/ddea2e4b53b6b2cfdd0d13c6beaac0978330c2a2 2012-09-15T07:33
--- include/xar.h.in.orig	2019-02-14 18:05:37.000000000 -0600
+++ include/xar.h.in	2022-03-10 06:07:31.000000000 -0600
@@ -134,6 +134,8 @@
 #define XAR_OPT_VAL_TRUE       "true"
 #define XAR_OPT_VAL_FALSE      "false"
 
+#define XAR_OPT_EXTRACTSTDOUT  "extract-stdout" /* Extract data to stdout instead of file (true/false) */
+
 /* xar signing algorithms */
 #define XAR_SIG_SHA1RSA		1
 
--- lib/archive.c.orig	2022-03-14 05:57:47.000000000 -0500
+++ lib/archive.c	2022-03-14 06:03:01.000000000 -0500
@@ -886,6 +886,9 @@
 	if( (strcmp(option, XAR_OPT_TOCCKSUM) == 0) ) {
 		XAR(x)->heap_offset = xar_io_get_toc_checksum_length_for_type(value);
 	}
+	if ((strcmp(option, XAR_OPT_EXTRACTSTDOUT) == 0)) {
+		XAR(x)->tostdout = strcmp(value, XAR_OPT_VAL_TRUE) == 0;
+	}
 	
 	/*	This was an edit from xar-1.4
 		Looks like we would only allow one definition for a particular key in this list
@@ -1499,33 +1502,46 @@
 	xar_file_t tmpf;
 	uint32_t result = -1;
 	
-	if( (strstr(XAR_FILE(f)->fspath, "/") != NULL) && (stat(XAR_FILE(f)->fspath, &sb)) && (XAR_FILE(f)->parent_extracted == 0) ) {
-		tmp1 = strdup(XAR_FILE(f)->fspath);
-		dname = xar_safe_dirname(tmp1);
-		tmpf = xar_file_find(XAR(x)->files, dname);
-		free(dname);
-		free(tmp1);
-		if( !tmpf ) {
-			xar_err_set_string(x, "Unable to find file");
-			xar_err_callback(x, XAR_SEVERITY_NONFATAL, XAR_ERR_ARCHIVE_EXTRACTION);
-			return -1;
-		}
+	if (XAR(x)->tostdout) {
+		char *buffer = NULL;
+		size_t bsize = 0;
+		int32_t result;
+		if ((result = xar_extract_tobuffersz(x, f, &buffer, &bsize)) != 0)
+			return result;
+		if (bsize && buffer && fwrite(buffer, bsize, 1, stdout) != 1)
+			result = -1;
+		free(buffer);
+		return result;
+	}
+	else {
+		if( (strstr(XAR_FILE(f)->fspath, "/") != NULL) && (stat(XAR_FILE(f)->fspath, &sb)) && (XAR_FILE(f)->parent_extracted == 0) ) {
+			tmp1 = strdup(XAR_FILE(f)->fspath);
+			dname = xar_safe_dirname(tmp1);
+			tmpf = xar_file_find(XAR(x)->files, dname);
+			free(dname);
+			free(tmp1);
+			if( !tmpf ) {
+				xar_err_set_string(x, "Unable to find file");
+				xar_err_callback(x, XAR_SEVERITY_NONFATAL, XAR_ERR_ARCHIVE_EXTRACTION);
+				return -1;
+			}
 		
-		XAR_FILE(f)->parent_extracted++;
-		result = xar_extract(x, tmpf);
+			XAR_FILE(f)->parent_extracted++;
+			result = xar_extract(x, tmpf);
 		
-		if (result < 0)
-			return result;
+			if (result < 0)
+				return result;
 			
-	}
+		}
 	
-	char* safe_path = xar_get_safe_path(f);
-	if (safe_path) {
-		result = xar_extract_tofile(x, f, safe_path);
-		free(safe_path);
-	}
+		char* safe_path = xar_get_safe_path(f);
+		if (safe_path) {
+			result = xar_extract_tofile(x, f, safe_path);
+			free(safe_path);
+		}
 	
-	return result;
+		return result;
+	}
 }
 
 int32_t xar_verify_progress(xar_t x, xar_file_t f, xar_progress_callback p) {
--- lib/archive.h.orig	2022-03-10 05:12:27.000000000 -0600
+++ lib/archive.h	2022-03-10 05:45:47.000000000 -0600
@@ -101,6 +101,7 @@
 	int toc_hash_size;			/* size of toc hash that was copied during archive open */
 	void *toc_hash;				/* copy of the toc hash copied during archive open */
 	int skipwarn;
+	int tostdout;
 	struct stat sbcache;
 };
 
--- src/xar.c.orig	2022-03-10 05:12:27.000000000 -0600
+++ src/xar.c	2022-03-10 05:39:41.000000000 -0600
@@ -53,8 +53,10 @@
 #include "config.h"
 #include "../lib/filetree.h"
 #include "util.h"
+#include "xar.h"
 #define SYMBOLIC 1
 #define NUMERIC  2
+#define XAR_OPT_EXTRACTSTDOUT  "extract-stdout" /* Extract data to stdout instead of file (true/false) */
 static int Perms = 0;
 static int Local = 0;
 static char *Subdoc = NULL;
@@ -73,6 +73,7 @@
 static int LinkSame = 0;
 static int NoOverwrite = 0;
 static int SaveSuid = 0;
+static int ToStdout = 0;
 
 struct lnode {
 	char *str;
@@ -383,6 +384,9 @@
 	if( SaveSuid ) {
 		xar_opt_set(x, XAR_OPT_SAVESUID, XAR_OPT_VAL_TRUE);
 	}
+	if (ToStdout) {
+		xar_opt_set(x, XAR_OPT_EXTRACTSTDOUT, XAR_OPT_VAL_TRUE);
+	}
 	
 	iter = xar_iter_new();
 	if( !iter ) {
@@ -457,24 +461,28 @@
 		
 		if( matched ) {
 			struct stat sb;
-			if( NoOverwrite && (lstat(path, &sb) == 0) ) {
+			if( !ToStdout && NoOverwrite && (lstat(path, &sb) == 0) ) {
 				printf("%s already exists, not overwriting\n", path);
 			} else {
 				const char *prop = NULL;
 				int deferred = 0;
 				if( xar_prop_get(f, "type", &prop) == 0 && prop != NULL ) {
 					if( strcmp(prop, "directory") == 0 ) {
-						struct lnode *tmpl = calloc(sizeof(struct lnode),1);
-						tmpl->str = (char *)f;
-						tmpl->next = dirs;
-						dirs = tmpl;
-						deferred = 1;
+						if (!ToStdout) {
+							struct lnode *tmpl = calloc(sizeof(struct lnode),1);
+							tmpl->str = (char *)f;
+							tmpl->next = dirs;
+							dirs = tmpl;
+							deferred = 1;
+						}
 					}
 				}
 				if( ! deferred ) {
-					files_extracted++;
 					print_file(x, f);
-					xar_extract(x, f);
+					if (xar_extract(x, f) == 0)
+						files_extracted++;
+					else if (!ToStdout)
+						fprintf(stderr, "Unable to extract file %s\n", path);
 				}
 			}
 		}
@@ -859,6 +867,8 @@
 	fprintf(stderr, "\t                      to a document in cwd named <name>.xml\n");
 	fprintf(stderr, "\t--exclude        POSIX regular expression of files to \n");
 	fprintf(stderr, "\t                      ignore while archiving.\n");
+	fprintf(stderr, "\t--to-stdout      Write file contents to standard out when extracting\n");
+	fprintf(stderr, "\t-O               Synonym for \"--to-stdout\"\n");
 	fprintf(stderr, "\t--rsize          Specifies the size of the buffer used\n");
 	fprintf(stderr, "\t                      for read IO operations in bytes.\n");
 	fprintf(stderr, "\t--coalesce-heap  When archived files are identical, only store one copy\n");
@@ -917,6 +927,7 @@
 		{"keep-existing",    no_argument,       0, 15},
 		{"keep-setuid",      no_argument,       0, 16},
 		{"compression-args", required_argument, 0, 17},
+		{"to-stdout",        no_argument,       0, 'O'},
 		{ 0, 0, 0, 0}
 	};
 
@@ -925,7 +936,7 @@
 		exit(1);
 	}
 
-	while( (c = getopt_long(argc, argv, "axcC:vtjzf:hpPln:s:d:vk", o, &loptind)) != -1 ) {
+	while( (c = getopt_long(argc, argv, "axcOC:vtjzf:hpPln:s:d:vk", o, &loptind)) != -1 ) {
 		switch(c) {
 		case  1 : // toc-cksum
 			if( !optarg ) {
@@ -1150,6 +1161,9 @@
 		case 'l': // stay on local device
 			Local = 1;
 			break;
+		case 'O':
+			ToStdout = 1;
+			break;
 		case 'n': // provide subdocument name
 			SubdocName = optarg;
 			break;
--- src/xar.1.orig	2020-05-12 22:28:17.000000000 -0500
+++ src/xar.1	2022-03-09 19:52:00.000000000 -0600
@@ -103,6 +103,13 @@
 the archive during creation or from being extracted during extraction.  
 This option can be specified multiple times.
 .TP
+\-\-to\-stdout
+Instead of creating files during extraction, write the file contents to standard output.
+Only the file data will be written to standard output.  All extended attributes, resource forks and other file properties are ignored with this option.
+.TP
+\-O
+Synonym for \-\-to\-stdout
+.TP
 \-\-rsize
 Specifies a size (in bytes) for the internal libxar read buffer while performing I/O.
 .TP