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trl — transform lists of strings

trl is a Unix CLI that ***tr***ansforms ***l***ists of quoted and/or unquoted strings, by default between single- and multi-line forms.

Both single- and double-quotes are recognized as input field (item) delimiters, and embedded quotes of the same type must be \-escaped.

Separators, delimiters, and wrapper strings are configurable, allowing for flexible transformations (reformatting) to and from a wide range of simple formats.


  • In the input, for embedded quotes of the same type to be properly
    recognized as literals inside quoted tokens, they must be

  • However, with multi-line input, if a given line is not quoted as a whole,
    backslash-escaping is implicitly applied to any single- or double-quotes
    on the line, allowing lines with imbalanced quotes, such as Ten o'clock.
    By contrast, if your input lines each contain multiple, individually quoted
    tokens, use -x to suppress this behavior; otherwise, such lines will be
    treated as a single token each, with embedded quotes escaped on output.

  • CAVEAT: Malformed input can result in LOSS OF TOKENS on output.

  • Similarly, on output, embedded instances of the output delimiters are

Input is provided via one or more arguments, or via stdin.

See the examples below, concise usage information further below, or read the manual.


  # Single-line list to multi-line list: 
$ trl '"one", "two", "three \" of rain"'
three " of rain
  # List to C-style array:
$ trl -S ', ' -D \" -W '{  }' one two three 'four (4)'
"one""two""three""four (4)" }
  # Multi-line to single-line:
$ trl <<EOF
three " of rain
"one""two""three \" of rain"
  # Multi-line list with multiple items each to Python array; 
  # note the use of -x to ensure that the indvidually quoted 
  # tokens are properly recognized.  
$ trl -x -s ' ' -S '' -D \' -W '[]' <<EOF
one "two (2)"
three 'four'
['one''two (2)''three''four']
  # US-format telephone number to CSV: 
$ trl -s '[() -]' -S , '(789) 123-456'


Supported platforms

  • When installing from the npm registry: Linux and OSX, with Perl installed (Perl comes with OSX, as do most Linux distros).
  • When installing manually: any Unix-like platform with Bash and Perl.

Installation from the npm registry

Note: Even if you don't use Node.js, its package manager, npm, works across platforms and is easy to install; try curl -L | bash

With Node.js or io.js installed, install the package as follows:

[sudo] npm install trl -g


  • Whether you need sudo depends on how you installed Node.js / io.js and whether you've changed permissions later; if you get an EACCES error, try again with sudo.
  • The -g ensures global installation and is needed to put trl in your system's $PATH.

Manual installation

  • Download the CLI as trl.
  • Make it executable with chmod +x trl.
  • Move it or symlink it to a folder in your $PATH, such as /usr/local/bin (OSX) or /usr/bin (Linux).


Find concise usage information below; for complete documentation, read the manual online, or, once installed, run man trl (trl --man if installed manually).

$ trl --help
Transforms lists of unquoted and/or quoted strings.
    trl [<options>] [<text>...]
    -s <inSep>      input list separator
    -S <outSep>     output list separator
    -k              keep input item delimiters
    -D <outDelim>   output item delimiter (cannot be combined with -k)
    -W <wrapText>   text to wrap the result list in
    -R <ors>        output record separator (multi-line + multi-item-per-line
                    input only)
    -x              do not auto-escape quotes on lines not quoted as a whole
By default,
 * a multi-line list is transformed to a single-line list with double-quoted  
   items separated by a comma followed by a space.
 * a single-line list is transformed to a multi-line list with unquoted items.
Standard options: --help, --man, --version, --home


Copyright (c) 2015-2016 Michael Klement (, released under the MIT license.


This project gratefully depends on the following open-source components, according to the terms of their respective licenses.

npm dependencies below have optional suffixes denoting the type of dependency; the absence of a suffix denotes a required run-time dependency: (D) denotes a development-time-only dependency, (O) an optional dependency, and (P) a peer dependency.

npm dependencies


Versioning complies with semantic versioning (semver).

  • v0.4.0 (2016-06-04):

    • [breaking change, enhancement] embedded instances of output separators are now get \-escaped on output.
    • [breaking change, enhancement] for multi-line input, any line that isn't quoted as a whole is now by default interpreted as a single token whose embedded quotes, if any, are treated as literals; use -x to suppress this behavior (assumes that your lines contain multiple, indvidually quoted tokens whose embedded quotes of the same type, if any, are \-escaped).
  • v0.3.3 (2015-09-19):

    • [doc] trl now has a man page (if manually installed, use trl --man); trl -h now just prints concise usage information.
  • v0.3.2 (2015-09-15):

    • [dev] Makefile improvements; various other behind-the-scenes tweaks.
  • v0.3.1 (2015-06-24):

    • [doc] Copy-editing of CLI help and read-me.
  • v0.3.0 (2015-06-24):

    • [new feature, behavior change] The output-delimiter string passed to -D may now be a symmetrical multi-character string such as (), in which case the 1st half acts as the opening delimiter, and the 2nd half as the closing delimiter.
    • [new feature, behavior change] The wrapper string passed to -W may now be a single character (in addition to a symmetrical multi-char. string), in which case that same character is used as both the opening and closing wrapper text.
  • v0.2.0 (2015-06-23):

    • [fix resulting in behavior change] Specifying a multi-line list as the only operand (e.g., trl <<<$'line 1\nline 2\nline 3' now behaves the same as passing the same string via stdin; i.e., in both cases, the result is a single-line list.
  • v0.1.1 (2015-06-14):

    • [doc] Fixed formatting of examples.
  • v0.1.0 (2015-06-14):

    • Initial release.

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