percol adds flavor of interactive selection to the traditional pipe concept on UNIX.

Code Quality Rank: L4
Programming language: Python
License: MIT License
Latest version: v0.2.1

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percol adds flavor of interactive selection to the traditional pipe concept on UNIX.

What's this


percol is an interactive grep tool in your terminal. percol

  1. receives input lines from stdin or a file,
  2. lists up the input lines,
  3. waits for your input that filter/select the line(s),
  4. and finally outputs the selected line(s) to stdout.

Since percol just filters the input and output the result to stdout, it can be used in command-chains with | in your shell (UNIX philosophy!).


  • Efficient: With lazy loads of input lines and query caching, percol handles huge inputs efficiently.
  • Customizable: Through configuration file (rc.py), percol's behavior including prompts, keymaps, and color schemes can be heavily customizable.
  • Migemo support: By supporting C/Migemo, percol filters Japanese inputs blazingly fast.

Related projects


percol currently supports only Python 2.x.


$ sudo pip install percol


First, clone percol repository and go into the directory.

$ git clone git://github.com/mooz/percol.git
$ cd percol

Then, run a command below.

$ sudo python setup.py install

If you don't have a root permission (or don't wanna install percol with sudo), try next one.

$ python setup.py install --prefix=~/.local
$ export PATH=~/.local/bin:$PATH


Specifying a filename.

$ percol /var/log/syslog

Specifying a redirection.

$ ps aux | percol


Interactive pgrep / pkill

Here is an interactive version of pgrep,

$ ps aux | percol | awk '{ print $2 }'

and here is an interactive version of pkill.

$ ps aux | percol | awk '{ print $2 }' | xargs kill

For zsh users, command versions are here (ppkill accepts options like -9).

function ppgrep() {
    if [[ $1 == "" ]]; then
        PERCOL="percol --query $1"
    ps aux | eval $PERCOL | awk '{ print $2 }'

function ppkill() {
    if [[ $1 =~ "^-" ]]; then
        QUERY=""            # options only
        QUERY=$1            # with a query
        [[ $# > 0 ]] && shift
    ppgrep $QUERY | xargs kill $*

zsh history search

In your .zshrc, put the lines below.

function exists { which $1 &> /dev/null }

if exists percol; then
    function percol_select_history() {
        local tac
        exists gtac && tac="gtac" || { exists tac && tac="tac" || { tac="tail -r" } }
        BUFFER=$(fc -l -n 1 | eval $tac | percol --query "$LBUFFER")
        CURSOR=$#BUFFER         # move cursor
        zle -R -c               # refresh

    zle -N percol_select_history
    bindkey '^R' percol_select_history

Then, you can display and search your zsh histories incrementally by pressing Ctrl + r key.


Here are some examples of tmux and percol integration.

bind b split-window "tmux lsw | percol --initial-index $(tmux lsw | awk '/active.$/ {print NR-1}') | cut -d':' -f 1 | tr -d '\n' | xargs -0 tmux select-window -t"
bind B split-window "tmux ls | percol --initial-index $(tmux ls | awk \"/^$(tmux display-message -p '#{session_name}'):/ {print NR-1}\") | cut -d':' -f 1 | tr -d '\n' | xargs -0 tmux switch-client -t"

By putting above 2 settings into tmux.conf, you can select a tmux window with ${TMUX_PREFIX} b keys and session with ${TMUX_PREFIX} B keys.

Attaching to running tmux sessions can also be made easier with percol with this function(tested to work in bash and zsh)

function pattach() {
    if [[ $1 == "" ]]; then
        PERCOL="percol --query $1"

    sessions=$(tmux ls)
    [ $? -ne 0 ] && return

    session=$(echo $sessions | eval $PERCOL | cut -d : -f 1)
    if [[ -n "$session" ]]; then
        tmux att -t $session

Calling percol from Python

Even though Percol is mainly designed as a UNIX command line tool, you can call it from your Python code like so:

from cStringIO import StringIO
from percol import Percol
from percol.actions import no_output

def main(candidates):
    si, so, se = StringIO(), StringIO(), StringIO()
    with Percol(
            descriptors={'stdin': si, 'stdout': so, 'stderr': se},
            candidates=iter(candidates)) as p:
    results = p.model_candidate.get_selected_results_with_index()
    return [r[0] for r in results]

if __name__ == "__main__":
    candidates = ['foo', 'bar', 'baz']
    results = main(candidates)
    print("You picked: {!r}".format(results))


Configuration file for percol should be placed under ${HOME}/.percol.d/ and named rc.py.

Here is an example ~/.percol.d/rc.py.

# X / _ / X
percol.view.PROMPT  = ur"<bold><yellow>X / _ / X</yellow></bold> %q"

# Emacs like
    "C-h" : lambda percol: percol.command.delete_backward_char(),
    "C-d" : lambda percol: percol.command.delete_forward_char(),
    "C-k" : lambda percol: percol.command.kill_end_of_line(),
    "C-y" : lambda percol: percol.command.yank(),
    "C-t" : lambda percol: percol.command.transpose_chars(),
    "C-a" : lambda percol: percol.command.beginning_of_line(),
    "C-e" : lambda percol: percol.command.end_of_line(),
    "C-b" : lambda percol: percol.command.backward_char(),
    "C-f" : lambda percol: percol.command.forward_char(),
    "M-f" : lambda percol: percol.command.forward_word(),
    "M-b" : lambda percol: percol.command.backward_word(),
    "M-d" : lambda percol: percol.command.delete_forward_word(),
    "M-h" : lambda percol: percol.command.delete_backward_word(),
    "C-n" : lambda percol: percol.command.select_next(),
    "C-p" : lambda percol: percol.command.select_previous(),
    "C-v" : lambda percol: percol.command.select_next_page(),
    "M-v" : lambda percol: percol.command.select_previous_page(),
    "M-<" : lambda percol: percol.command.select_top(),
    "M->" : lambda percol: percol.command.select_bottom(),
    "C-m" : lambda percol: percol.finish(),
    "C-j" : lambda percol: percol.finish(),
    "C-g" : lambda percol: percol.cancel(),

Customizing prompt

In percol, a prompt consists of two part: PROMPT and RPROMPT, like zsh. As the following example shows, each part appearance can be customized by specifying a prompt format into percol.view.PROMPT and percol.view.RPROMPT respectively.

percol.view.PROMPT = ur"<blue>Input:</blue> %q"
percol.view.RPROMPT = ur"(%F) [%i/%I]"

In prompt formats, a character preceded by % indicates a prompt format specifier and is expanded into a corresponding system value.

  • %%
    • Display % itself
  • %q
    • Display query and caret
  • %Q
    • Display query without caret
  • %n
    • Page number
  • %N
    • Total page number
  • %i
    • Current line number
  • %I
    • Total line number
  • %c
    • Caret position
  • %k
    • Last input key

Dynamic prompt

By changing percol.view.PROMPT into a getter, percol prompts becomes more fancy.

# Change prompt in response to the status of case sensitivity
percol.view.__class__.PROMPT = property(
    lambda self:
    ur"<bold><blue>QUERY </blue>[a]:</bold> %q" if percol.model.finder.case_insensitive
    else ur"<bold><green>QUERY </green>[A]:</bold> %q"

Custom format specifiers

# Display finder name in RPROMPT
percol.view.prompt_replacees["F"] = lambda self, **args: self.model.finder.get_name()
percol.view.RPROMPT = ur"(%F) [%i/%I]"

Customizing styles

For now, styles of following 4 items can be customized in rc.py.

percol.view.CANDIDATES_LINE_BASIC    = ("on_default", "default")
percol.view.CANDIDATES_LINE_SELECTED = ("underline", "on_yellow", "white")
percol.view.CANDIDATES_LINE_MARKED   = ("bold", "on_cyan", "black")
percol.view.CANDIDATES_LINE_QUERY    = ("yellow", "bold")

Each RHS is a tuple of style specifiers listed below.

Foreground Colors

  • "black" for curses.COLOR_BLACK
  • "red" for curses.COLOR_RED
  • "green" for curses.COLOR_GREEN
  • "yellow" for curses.COLOR_YELLOW
  • "blue" for curses.COLOR_BLUE
  • "magenta" for curses.COLOR_MAGENTA
  • "cyan" for curses.COLOR_CYAN
  • "white" for curses.COLOR_WHITE

Background Color

  • "on_black" for curses.COLOR_BLACK
  • "on_red" for curses.COLOR_RED
  • "on_green" for curses.COLOR_GREEN
  • "on_yellow" for curses.COLOR_YELLOW
  • "on_blue" for curses.COLOR_BLUE
  • "on_magenta" for curses.COLOR_MAGENTA
  • "on_cyan" for curses.COLOR_CYAN
  • "on_white" for curses.COLOR_WHITE


  • "altcharset" for curses.A_ALTCHARSET
  • "blink" for curses.A_BLINK
  • "bold" for curses.A_BOLD
  • "dim" for curses.A_DIM
  • "normal" for curses.A_NORMAL
  • "standout" for curses.A_STANDOUT
  • "underline" for curses.A_UNDERLINE
  • "reverse" for curses.A_REVERSE

Matching Method

By default, percol interprets input queries by users as string. If you prefer regular expression, try --match-method command line option.

$ percol --match-method regex

Migemo support

percol supports migemo (http://0xcc.net/migemo/) matching, which allows us to search Japanese documents with ASCII characters.

$ percol --match-method migemo

To use this feature, you need to install C/Migemo (https://github.com/koron/cmigemo). In Ubuntu, it's simple:

$ sudo apt-get install cmigemo

After that, by specifying a command line argument --match-method migemo, you can use migemo in percol.

NOTE: This feature uses python-cmigemo package (https://github.com/mooz/python-cmigemo). Doing pip install percol also installs this package too.

Dictionary settings

By default, percol assumes the path of a dictionary for migemo is /usr/local/share/migemo/utf-8/migemo-dict. If the dictionary is located in a different place, you should tell the location via rc.py.

For example, if the path of the dictionary is /path/to/a/migemo-dict, put lines below into your rc.py.

from percol.finder import FinderMultiQueryMigemo
FinderMultiQueryMigemo.dictionary_path = "/path/to/a/migemo-dict"

Minimum query length

If the query length is too short, migemo generates very long regular expression. To deal with this problem, percol does not pass a query if the length of the query is shorter than 2 and treat the query as raw regular expression.

To change this behavior, change the value of FinderMultiQueryMigemo.minimum_query_length like following settings.

from percol.finder import FinderMultiQueryMigemo
FinderMultiQueryMigemo.minimum_query_length = 1

Pinyin support

Now percol supports pinyin (http://en.wikipedia.org/wiki/Pinyin) for matching Chinese characters.

$ percol --match-method pinyin

In this matching method, first char of each Chinese character's pinyin sequence is used for matching. For example, 'zw' matches '中文' (ZhongWen), '中午'(ZhongWu), '作为' (ZuoWei) etc.

Extra package pinin(https://pypi.python.org/pypi/pinyin/0.2.5) needed.

Switching matching method dynamically

Matching method can be switched dynamically (at run time) by executing percol.command.specify_finder(FinderClass) or percol.command.toggle_finder(FinderClass). In addition, percol.command.specify_case_sensitive(case_sensitive) and percol.command.toggle_case_sensitive() change the matching status of case sensitivity.

from percol.finder import FinderMultiQueryMigemo, FinderMultiQueryRegex
    "M-c" : lambda percol: percol.command.toggle_case_sensitive(),
    "M-m" : lambda percol: percol.command.toggle_finder(FinderMultiQueryMigemo),
    "M-r" : lambda percol: percol.command.toggle_finder(FinderMultiQueryRegex)


Selecting multiple candidates

You can select and let percol to output multiple candidates by percol.command.toggle_mark_and_next() (which is bound to C-SPC by default).

percol.command.mark_all(), percol.command.unmark_all() and percol.command.toggle_mark_all() are useful to mark / unmark all candidates at once.

Z Shell support

A zsh completing-function for percol is available in https://github.com/mooz/percol/blob/master/tools/zsh/_percol .