diff options
Diffstat (limited to 'programs')
| -rw-r--r-- | programs/lz4.1.md | 27 | ||||
| -rw-r--r-- | programs/lz4cli.c | 37 |
2 files changed, 39 insertions, 25 deletions
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(); |