Merge pull request #686 from lz4/clistdout

cli: warning for stdout as default output

4 files changed, 62 insertions, 46 deletions

diff --git a/.travis.yml b/.travis.yml
index 301d294..2065478 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -8,7 +8,7 @@ matrix:
       os: osx
       compiler: clang
       script:
-        - make -C tests test-lz4 MOREFLAGS='-Werror -Wconversion -Wno-sign-conversion'
+        - make -C tests test-lz4 MOREFLAGS='-Werror -Wconversion -Wno-sign-conversion' | tee # test scenario where `stdout` is not the console
         - CFLAGS=-m32 make -C tests clean test-lz4-contentSize
 
     # Container-based 12.04 LTS Server Edition 64 bit (doesn't support 32-bit includes)
diff --git a/programs/lz4.1.md b/programs/lz4.1.md
index 10449a0..ffda3ff 100644
--- a/programs/lz4.1.md
+++ b/programs/lz4.1.md
@@ -31,29 +31,29 @@ The native file format is the `.lz4` format.
 `lz4` supports a command line syntax similar _but not identical_ to `gzip(1)`.
 Differences are :
 
-  * `lz4` preserves original files
   * `lz4` compresses a single file by default (see `-m` for multiple files)
   * `lz4 file1 file2` means : compress file1 _into_ file2
   * `lz4 file.lz4` will default to decompression (use `-z` to force compression)
+  * `lz4` preserves original files
   * `lz4` shows real-time notification statistics
      during compression or decompression of a single file
      (use `-q` to silence them)
-  * If no destination name is provided, result is sent to `stdout`
-    _except if stdout is the console_.
-  * If no destination name is provided, __and__ if `stdout` is the console,
-    `file` is compressed into `file.lz4`.
-  * As a consequence of previous rules, note the following example :
-    `lz4 file | consumer` sends compressed data to `consumer` through `stdout`,
-    hence it does _not_ create `file.lz4`.
-  * Another consequence of those rules is that to run `lz4` under `nohup`,
-    you should provide a destination file: `nohup lz4 file file.lz4`,
-    because `nohup` writes the specified command's output to a file.
+  * When no destination is specified, result is sent on implicit output,
+    which depends on `stdout` status.
+    When `stdout` _is Not the console_, it becomes the implicit output.
+    Otherwise, if `stdout` is the console, the implicit output is `filename.lz4`.
+  * It is considered bad practice to rely on implicit output in scripts.
+    because the script's environment may change.
+    Always use explicit output in scripts.
+    `-c` ensures that output will be `stdout`.
+    Conversely, providing a destination name, or using `-m`
+    ensures that the output will be either the specified name, or `filename.lz4` respectively.
 
 Default behaviors can be modified by opt-in commands, detailed below.
 
   * `lz4 -m` makes it possible to provide multiple input filenames,
     which will be compressed into files using suffix `.lz4`.
-    Progress notifications are also disabled by default (use `-v` to enable them).
+    Progress notifications become disabled by default (use `-v` to enable them).
     This mode has a behavior which more closely mimics `gzip` command line,
     with the main remaining difference being that source files are preserved by default.
   * Similarly, `lz4 -m -d` can decompress multiple `*.lz4` files.
@@ -81,8 +81,7 @@ In some cases, some options can be expressed using short command `-x`
 or long command `--long-word`.
 Short commands can be concatenated together.
 For example, `-d -c` is equivalent to `-dc`.
-Long commands cannot be concatenated.
-They must be clearly separated by a space.
+Long commands cannot be concatenated. They must be clearly separated by a space.
 
 ### Multiple commands
 
diff --git a/programs/lz4cli.c b/programs/lz4cli.c
index 8bd7042..82f2fac 100644
--- a/programs/lz4cli.c
+++ b/programs/lz4cli.c
@@ -652,7 +652,16 @@ int main(int argc, const char** argv)
 
     /* No output filename ==> try to select one automatically (when possible) */
     while ((!output_filename) && (multiple_inputs==0)) {
-        if (!IS_CONSOLE(stdout)) { output_filename=stdoutmark; break; }   /* Default to stdout whenever possible (i.e. not a console) */
+
+        if (!IS_CONSOLE(stdout)) {
+            /* Default to stdout whenever stdout is not the console.
+             * Note : this policy may change in the future, therefore don't rely on it !
+             * To ensure `stdout` is explicitly selected, use `-c` command flag.
+             * Conversely, to ensure output will not become `stdout`, use `-m` command flag */
+            DISPLAYLEVEL(1, "Warning : using stdout as default output. Do not rely on this behavior: use explicit `-c` instead ! \n");
+            output_filename=stdoutmark;
+            break;
+        }
         if (mode == om_auto) {  /* auto-determine compression or decompression, based on file extension */
             mode = determineOpMode(input_filename);
         }
@@ -682,10 +691,14 @@ int main(int argc, const char** argv)
         break;
     }
 
-    /* Check if output is defined as console; trigger an error in this case */
+    if (multiple_inputs==0) assert(output_filename);
+    /* when multiple_inputs==1, output_filename may simply be useless,
+     * however, output_filename must be !NULL for next strcmp() tests */
     if (!output_filename) output_filename = "*\\dummy^!//";
+
+    /* Check if output is defined as console; trigger an error in this case */
     if (!strcmp(output_filename,stdoutmark) && IS_CONSOLE(stdout) && !forceStdout) {
-        DISPLAYLEVEL(1, "refusing to write to console without -c\n");
+        DISPLAYLEVEL(1, "refusing to write to console without -c \n");
         exit(1);
     }
     /* Downgrade notification level in stdout and multiple file mode */
@@ -701,21 +714,23 @@ int main(int argc, const char** argv)
     LZ4IO_setNotificationLevel((int)displayLevel);
     if (ifnIdx == 0) multiple_inputs = 0;
     if (mode == om_decompress) {
-        if (multiple_inputs)
-            operationResult = LZ4IO_decompressMultipleFilenames(prefs, inFileNames, ifnIdx, !strcmp(output_filename,stdoutmark) ? stdoutmark : LZ4_EXTENSION);
-        else
+        if (multiple_inputs) {
+            assert(ifnIdx <= INT_MAX);
+            operationResult = LZ4IO_decompressMultipleFilenames(prefs, inFileNames, (int)ifnIdx, !strcmp(output_filename,stdoutmark) ? stdoutmark : LZ4_EXTENSION);
+        } else {
             operationResult = DEFAULT_DECOMPRESSOR(prefs, input_filename, output_filename);
+        }
     } else {   /* compression is default action */
         if (legacy_format) {
             DISPLAYLEVEL(3, "! Generating LZ4 Legacy format (deprecated) ! \n");
             LZ4IO_compressFilename_Legacy(prefs, input_filename, output_filename, cLevel);
         } else {
-            if (multiple_inputs)
-                operationResult = LZ4IO_compressMultipleFilenames(prefs, inFileNames, ifnIdx, !strcmp(output_filename,stdoutmark) ? stdoutmark : LZ4_EXTENSION, cLevel);
-            else
+            if (multiple_inputs) {
+                assert(ifnIdx <= INT_MAX);
+                operationResult = LZ4IO_compressMultipleFilenames(prefs, inFileNames, (int)ifnIdx, !strcmp(output_filename,stdoutmark) ? stdoutmark : LZ4_EXTENSION, cLevel);
+            } else {
                 operationResult = DEFAULT_COMPRESSOR(prefs, input_filename, output_filename, cLevel);
-        }
-    }
+    }   }   }
 
 _cleanup:
     if (main_pause) waitEnter();
diff --git a/tests/Makefile b/tests/Makefile
index 70cae63..ddc6d1e 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -144,6 +144,8 @@ ifneq (,$(filter $(shell uname), Darwin ))
 MD5:=md5 -r
 endif
 
+# note : we should probably settle on a single compare utility
+CMP:=cmp
 DIFF:=diff
 ifneq (,$(filter $(shell uname),SunOS))
 DIFF:=gdiff
@@ -176,15 +178,15 @@ test-install: lz4 lib liblz4.pc
 test-lz4-sparse: lz4 datagen
 	@echo "\n ---- test sparse file support ----"
 	./datagen -g5M  -P100 > tmplsdg5M
-	$(LZ4) -B4D tmplsdg5M | $(LZ4) -dv --sparse > tmplscB4
+	$(LZ4) -B4D tmplsdg5M -c | $(LZ4) -dv --sparse > tmplscB4
 	$(DIFF) -s tmplsdg5M tmplscB4
-	$(LZ4) -B5D tmplsdg5M | $(LZ4) -dv --sparse > tmplscB5
+	$(LZ4) -B5D tmplsdg5M -c | $(LZ4) -dv --sparse > tmplscB5
 	$(DIFF) -s tmplsdg5M tmplscB5
-	$(LZ4) -B6D tmplsdg5M | $(LZ4) -dv --sparse > tmplscB6
+	$(LZ4) -B6D tmplsdg5M -c | $(LZ4) -dv --sparse > tmplscB6
 	$(DIFF) -s tmplsdg5M tmplscB6
-	$(LZ4) -B7D tmplsdg5M | $(LZ4) -dv --sparse > tmplscB7
+	$(LZ4) -B7D tmplsdg5M -c | $(LZ4) -dv --sparse > tmplscB7
 	$(DIFF) -s tmplsdg5M tmplscB7
-	$(LZ4) tmplsdg5M | $(LZ4) -dv --no-sparse > tmplsnosparse
+	$(LZ4) tmplsdg5M -c | $(LZ4) -dv --no-sparse > tmplsnosparse
 	$(DIFF) -s tmplsdg5M tmplsnosparse
 	ls -ls tmpls*
 	./datagen -s1 -g1200007 -P100 | $(LZ4) | $(LZ4) -dv --sparse > tmplsodd   # Odd size file (to generate non-full last block)
@@ -200,7 +202,7 @@ test-lz4-sparse: lz4 datagen
 	cat tmplsdg1M tmplsdg1M > tmpls2M
 	$(LZ4) -B5 -v tmplsdg1M tmplsc
 	$(LZ4) -d -v tmplsc tmplsr
-	$(LZ4) -d -v tmplsc >> tmplsr
+	$(LZ4) -d -v tmplsc -c >> tmplsr
 	ls -ls tmp*
 	$(DIFF) tmpls2M tmplsr
 	@$(RM) tmpls*
@@ -208,8 +210,8 @@ test-lz4-sparse: lz4 datagen
 test-lz4-contentSize: lz4 datagen
 	@echo "\n ---- test original size support ----"
 	./datagen -g15M > tmplc1
-	$(LZ4) -v tmplc1 | $(LZ4) -t
-	$(LZ4) -v --content-size tmplc1 | $(LZ4) -d > tmplc2
+	$(LZ4) -v tmplc1 -c | $(LZ4) -t
+	$(LZ4) -v --content-size tmplc1 -c | $(LZ4) -d > tmplc2
 	$(DIFF) -s tmplc1 tmplc2
 	@$(RM) tmplc*
 
@@ -218,11 +220,11 @@ test-lz4-frame-concatenation: lz4 datagen
 	@echo -n > tmp-lfc-empty
 	@echo hi > tmp-lfc-nonempty
 	cat tmp-lfc-nonempty tmp-lfc-empty tmp-lfc-nonempty > tmp-lfc-src
-	@$(LZ4) -zq tmp-lfc-empty > tmp-lfc-empty.lz4
-	@$(LZ4) -zq tmp-lfc-nonempty > tmp-lfc-nonempty.lz4
+	$(LZ4) -zq tmp-lfc-empty -c > tmp-lfc-empty.lz4
+	$(LZ4) -zq tmp-lfc-nonempty -c > tmp-lfc-nonempty.lz4
 	cat tmp-lfc-nonempty.lz4 tmp-lfc-empty.lz4 tmp-lfc-nonempty.lz4 > tmp-lfc-concat.lz4
-	$(LZ4) -d tmp-lfc-concat.lz4 > tmp-lfc-result
-	cmp tmp-lfc-src tmp-lfc-result
+	$(LZ4) -d tmp-lfc-concat.lz4 -c > tmp-lfc-result
+	$(CMP) tmp-lfc-src tmp-lfc-result
 	@$(RM) tmp-lfc-*
 	@echo frame concatenation test completed
 
@@ -241,15 +243,15 @@ test-lz4-multiple: lz4 datagen
 	mv tmp-tlm2 tmp-tlm2-orig
 	mv tmp-tlm3 tmp-tlm3-orig
 	$(LZ4) -d -f -m tmp-tlm*.lz4
-	cmp tmp-tlm1 tmp-tlm1-orig   # must be identical
-	cmp tmp-tlm2 tmp-tlm2-orig
-	cmp tmp-tlm3 tmp-tlm3-orig
+	$(CMP) tmp-tlm1 tmp-tlm1-orig   # must be identical
+	$(CMP) tmp-tlm2 tmp-tlm2-orig
+	$(CMP) tmp-tlm3 tmp-tlm3-orig
 	# compress multiple files into stdout
 	cat tmp-tlm1.lz4 tmp-tlm2.lz4 tmp-tlm3.lz4 > tmp-tlm-concat1
 	$(RM) *.lz4
 	$(LZ4) -m tmp-tlm1 tmp-tlm2 tmp-tlm3 -c > tmp-tlm-concat2
 	test ! -f tmp-tlm1.lz4  # must not create .lz4 artefact
-	cmp tmp-tlm-concat1 tmp-tlm-concat2  # must be equivalent
+	$(CMP) tmp-tlm-concat1 tmp-tlm-concat2  # must be equivalent
 	# decompress multiple files into stdout
 	$(RM) tmp-tlm-concat1 tmp-tlm-concat2
 	$(LZ4) -f -m tmp-tlm1 tmp-tlm2 tmp-tlm3   # generate .lz4 to decompress
@@ -257,7 +259,7 @@ test-lz4-multiple: lz4 datagen
 	$(RM) tmp-tlm1 tmp-tlm2 tmp-tlm3
 	$(LZ4) -d -m tmp-tlm1.lz4 tmp-tlm2.lz4 tmp-tlm3.lz4 -c > tmp-tlm-concat2
 	test ! -f tmp-tlm1  # must not create file artefact
-	cmp tmp-tlm-concat1 tmp-tlm-concat2  # must be equivalent
+	$(CMP) tmp-tlm-concat1 tmp-tlm-concat2  # must be equivalent
 	# compress multiple files, one of which is absent (must fail)
 	! $(LZ4) -f -m tmp-tlm-concat1 notHere tmp-tlm-concat2  # must fail : notHere not present
 	@$(RM) tmp-tlm*
@@ -315,7 +317,7 @@ test-lz4-basic: lz4 datagen unlz4 lz4cat
 	! $(LZ4) -c --fast=-1 tmp-tlb-dg20K # lz4 should fail when fast=-1
 	# Test for #596
 	@echo "TEST" > tmp-tlb-test
-	$(LZ4) tmp-tlb-test
+	$(LZ4) -m tmp-tlb-test
 	$(LZ4) tmp-tlb-test.lz4 tmp-tlb-test2
 	$(DIFF) -q tmp-tlb-test tmp-tlb-test2
 	@$(RM) tmp-tlb*
@@ -341,8 +343,8 @@ test-lz4-dict: lz4 datagen
 	for l in 0 1 4 128 32767 32768 32769 65535 65536 65537 98303 98304 98305 131071 131072 131073; do \
 		./datagen -g$$l > tmp-dict-$$l; \
 		$(DD) if=tmp-dict-$$l of=tmp-dict-$$l-tail bs=1 count=65536 skip=$$((l > 65536 ? l - 65536 : 0)); \
-		< tmp-dict-$$l      $(LZ4) -D stdin tmp-dict-data-128KB | $(LZ4) -dD tmp-dict-$$l-tail | $(DIFF) - tmp-dict-data-128KB; \
-		< tmp-dict-$$l-tail $(LZ4) -D stdin tmp-dict-data-128KB | $(LZ4) -dD tmp-dict-$$l      | $(DIFF) - tmp-dict-data-128KB; \
+		< tmp-dict-$$l      $(LZ4) -D stdin tmp-dict-data-128KB -c | $(LZ4) -dD tmp-dict-$$l-tail | $(DIFF) - tmp-dict-data-128KB; \
+		< tmp-dict-$$l-tail $(LZ4) -D stdin tmp-dict-data-128KB -c | $(LZ4) -dD tmp-dict-$$l      | $(DIFF) - tmp-dict-data-128KB; \
 	done
 
 	@$(RM) tmp-dict*