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Manual Reference Pages  -  RWCAT (1)

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rwcat - Concatenate SiLK Flow files into single stream



  rwcat [--output-path=FILE] [--note-add=TEXT] [--note-file-add=FILE]
        [--print-filenames] [--byte-order={big | little | native}]
        [--ipv4-output] [--compression-method=COMP_METHOD]
        {[--xargs] | [--xargs=FILENAME] | [FILE [FILE...]]}

  rwcat --help

  rwcat --version


rwcat reads SiLK Flow records and writes the records in the standard binary SiLK format to the specified output-path; rwcat will write the records to the standard output when stdout is not the terminal and --output-path is not provided.

rwcat reads SiLK Flow records from the files named on the command line or from the standard input when no file names are specified and --xargs is not present. To read the standard input in addition to the named files, use - or stdin as a file name. If an input file name ends in .gz, the file will be uncompressed as it is read. When the --xargs switch is provided, rwcat will read the names of the files to process from the named text file, or from the standard input if no file name argument is provided to the switch. The input to --xargs must contain one file name per line.

rwcat does not copy the invocation history and annotations (notes) from the header(s) of the source file(s) to the destination file. The --note-add or --note-file-add switch may be used to add a new annotation to the destination file.


Option names may be abbreviated if the abbreviation is unique or is an exact match for an option. A parameter to an option may be specified as --arg=param or --arg param, though the first form is required for options that take optional parameters.
--output-path=FILE Write the SiLK Flow records to FILE, which must not exist. If the switch is not provided or if FILE is stdout, flows are written to the standard output. If the name ends in .gz, the output will be compressed using gzip(1).
--note-add=TEXT Add the specified TEXT to the header of the output file as an annotation. This switch may be repeated to add multiple annotations to a file. To view the annotations, use the rwfileinfo(1) tool.
--note-file-add=FILENAME Open FILENAME and add the contents of that file to the header of the output file as an annotation. This switch may be repeated to add multiple annotations. Currently the application makes no effort to ensure that FILENAME contains text; be careful that you do not attempt to add a SiLK data file as an annotation.
--byte-order=ENDIAN Set the byte order for the output SiLK Flow records. The argument is one of the following:
native Use the byte order of the machine where rwcat is running. This is the default.
big Use network byte order (big endian) for the output.
little Write the output in little endian format.
--ipv4-output Force the output to contain only IPv4 flow records. When this switch is specified, IPv6 flow records that contain addresses in the ::ffff:0:0/96 prefix are converted to IPv4 and written to the output, and all other IPv6 records are ignored. When SiLK has not been compiled with IPv6 support, rwcat acts as if this switch were always in effect.
--compression-method=COMP_METHOD Specify how to compress the output. When this switch is not given, output to the standard output or to named pipes is not compressed, and output to files is compressed using the default chosen when SiLK was compiled. The valid values for COMP_METHOD are determined by which external libraries were found when SiLK was compiled. To see the available compression methods and the default method, use the --help or --version switch. SiLK can support the following COMP_METHOD values when the required libraries are available.
none Do not compress the output using an external library.
zlib Use the zlib(3) library for compressing the output, and always compress the output regardless of the destination. Using zlib produces the smallest output files at the cost of speed.
lzo1x Use the lzo1x algorithm from the LZO real time compression library for compression, and always compress the output regardless of the destination. This compression provides good compression with less memory and CPU overhead.
best Use lzo1x if available, otherwise use zlib. Only compress the output when writing to a file.
--print-filenames Print the names of input files and the number of records each file contains as the files are read.
--site-config-file=FILENAME Read the SiLK site configuration from the named file FILENAME. When this switch is not provided, rwcat searches for the site configuration file in the locations specified in the FILES section.
--xargs=FILENAME Causes rwcat to read file names from FILENAME or from the standard input if FILENAME is not provided. The input should have one file name per line. rwcat will open each file in turn and read records from it, as if the files had been listed on the command line.
--help Print the available options and exit.
--version Print the version number and information about how SiLK was configured, then exit the application.


In the following examples, the dollar sign ($) represents the shell prompt. The text after the dollar sign represents the command line. Lines have been wrapped for improved readability, and the back slash (\) is used to indicate a wrapped line.

To combine the results of several rwfilter(1) runs---stored in the files,, ... to create the file, you can use:

 $ rwcat  *.rw

If the shell complains about too many arguments, you can use the UNIX find(1) function and pipe its output to rwcat:

 $ find . -name *.rw -print                   \
   | rwcat --xargs


SILK_CLOBBER The SiLK tools normally refuse to overwrite existing files. Setting SILK_CLOBBER to a non-empty value removes this restriction.
SILK_CONFIG_FILE This environment variable is used as the value for the --site-config-file when that switch is not provided.
SILK_DATA_ROOTDIR This environment variable specifies the root directory of data repository. As described in the FILES section, rwcat may use this environment variable when searching for the SiLK site configuration file.
SILK_PATH This environment variable gives the root of the install tree. When searching for configuration files, rwcat may use this environment variable. See the FILES section for details.


/usr/local/share/silk.conf Possible locations for the SiLK site configuration file which are checked when the --site-config-file switch is not provided.


rwfilter(1), rwfileinfo(1), silk(7), gzip(1), find(1), zlib(3)


Although rwcat will read from the standard input, this feature should be used with caution. rwcat will treat the standard input as a single file, as it has no way to know when one file ends and the next begins. The following will not work:

 $ cat | rwcat     # WRONG!

The header of will be treated as data of, resulting in corrupt output.

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SiLK RWCAT (1) 2016-04-05

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