vimproc#system() don't work.vim

gistfile1.vim

echo 'executable():' executable('ctags')

echo 'system():' system('ctags --help')

echo 'vimproc#system()' vimproc#system('ctags --help')

finish
" ↑ の結果。

executable(): 1
system(): Exuberant Ctags 5.8J1, Copyright (C) 1996-2009 Darren Hiebert
  Compiled: Nov 29 2010, 19:13:41
  Addresses: <dhiebert@users.sourceforge.net>, http://ctags.sourceforge.net
  Japanese patch  by Hirohito Higashi <h_east@pop11.odn.ne.jp>
                     http://hp.vector.co.jp/authors/VA025040/
  Optional compiled features: +win32, +regex, +internal-sort, +kanji

Usage: ctags [options] [file(s)]

  -a   Append the tags to an existing tag file.
  -B   Use backward searching patterns (?...?).
  -e   Output tag file for use with Emacs.
  -f <name>
       Write tags to specified file. Value of "-" writes tags to stdout
       ["tags"; or "TAGS" when -e supplied].
  -F   Use forward searching patterns (/.../) (default).
  -h <list>
       Specify list of file extensions to be treated as include files.
       [".h.H.hh.hpp.hxx.h++"].
  -I <list|@file>
       A list of tokens to be specially handled is read from either the
       command line or the specified file.
  -L <file>
       A list of source file names are read from the specified file.
       If specified as "-", then standard input is read.
  -n   Equivalent to --excmd=number.
  -N   Equivalent to --excmd=pattern.
  -o   Alternative for -f.
  -R   Equivalent to --recurse.
  -u   Equivalent to --sort=no.
  -V   Equivalent to --verbose.
  -x   Print a tabular cross reference file to standard output.
  --append=[yes|no]
       Should tags should be appended to existing tag file [no]?
  --etags-include=file
      Include reference to 'file' in Emacs-style tag file (requires -e).
  --exclude=pattern
      Exclude files and directories matching 'pattern'.
  --excmd=number|pattern|mix
       Uses the specified type of EX command to locate tags [mix].
  --extra=[+|-]flags
      Include extra tag entries for selected information (flags: "fq").
  --fields=[+|-]flags
      Include selected extension fields (flags: "afmikKlnsStz") [fks].
  --file-scope=[yes|no]
       Should tags scoped only for a single file (e.g. "static" tags
       be included in the output [yes]?
  --filter=[yes|no]
       Behave as a filter, reading file names from standard input and
       writing tags to standard output [no].
  --filter-terminator=string
       Specify string to print to stdout following the tags for each file
       parsed when --filter is enabled.
  --format=level
       Force output of specified tag file format [2].
  --help
       Print this option summary.
  --if0=[yes|no]
       Should C code within #if 0 conditional branches be parsed [no]?
  --jcode=ascii|sjis|euc|utf8
       Specify Japanese kanji code [sjis].
  --<LANG>-kinds=[+|-]kinds
       Enable/disable tag kinds for language <LANG>.
  --langdef=name
       Define a new language to be parsed with regular expressions.
  --langmap=map(s)
       Override default mapping of language to source file extension.
  --language-force=language
       Force all files to be interpreted using specified language.
  --languages=[+|-]list
       Restrict files scanned for tags to those mapped to langauges
       specified in the comma-separated 'list'. The list can contain any
       built-in or user-defined language [all].
  --license
       Print details of software license.
  --line-directives=[yes|no]
       Should #line directives be processed [no]?
  --links=[yes|no]
       Indicate whether symbolic links should be followed [yes].
  --list-kinds=[language|all]
       Output a list of all tag kinds for specified language or all.
  --list-languages
       Output list of supported languages.
  --list-maps=[language|all]
       Output list of language mappings.
  --options=file
       Specify file from which command line options should be read.
  --recurse=[yes|no]
       Recurse into directories supplied on command line [no].
  --regex-<LANG>=/line_pattern/name_pattern/[flags]
       Define regular expression for locating tags in specific language.
  --sort=[yes|no|foldcase]
       Should tags be sorted (optionally ignoring case) [yes]?.
  --tag-relative=[yes|no]
       Should paths be relative to location of tag file [no; yes when -e]?
  --totals=[yes|no]
       Print statistics about source and tag files [no].
  --verbose=[yes|no]
       Enable verbose messages describing actions on each source file.
  --version
       Print version identifier to standard output.

vimproc#system()
function vimproc#system..<SNR>163_system..vimproc#pgroup_open..<SNR>163_pgroup_open..vimproc#plineop
en3..<SNR>163_plineopen..<SNR>163_convert_args..vimproc#get_command_name の処理中にエラーが検出され>
ました:
行   27:
E605: 例外が捕捉されませんでした: vimproc#get_command_name: File "ctags" is not found.
function vimproc#system..<SNR>163_system..vimproc#pgroup_open..<SNR>163_pgroup_open..vimproc#plineop
en3..<SNR>163_plineopen の処理中にエラーが検出されました: