Regular Expressions 101

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An explanation of your regex will be automatically generated as you type.
Detailed match information will be displayed here automatically.
  • All Tokens
  • Common Tokens
  • General Tokens
  • Anchors
  • Meta Sequences
  • Quantifiers
  • Group Constructs
  • Character Classes
  • Flags/Modifiers
  • Substitution
  • A single character of: a, b or c
    [abc]
  • A character except: a, b or c
    [^abc]
  • A character in the range: a-z
    [a-z]
  • A character not in the range: a-z
    [^a-z]
  • A character in the range: a-z or A-Z
    [a-zA-Z]
  • Any single character
    .
  • Alternate - match either a or b
    a|b
  • Any whitespace character
    \s
  • Any non-whitespace character
    \S
  • Any digit
    \d
  • Any non-digit
    \D
  • Any word character
    \w
  • Any non-word character
    \W
  • Non-capturing group
    (?:...)
  • Capturing group
    (...)
  • Zero or one of a
    a?
  • Zero or more of a
    a*
  • One or more of a
    a+
  • Exactly 3 of a
    a{3}
  • 3 or more of a
    a{3,}
  • Between 3 and 6 of a
    a{3,6}
  • Start of string
    ^
  • End of string
    $
  • A word boundary
    \b
  • Non-word boundary
    \B

Regular Expression

/
/
gm

Test String

Substitution

Processing...

Code Generator

Generated Code

$re = '/(^\w.*\n\n)+(^(##.*\n)+)/m'; $str = 'tab_bar_edge top ## Which edge to show the tab bar on, top or bottom tab_bar_margin_width 0.0 ## The margin to the left and right of the tab bar (in pts) tab_bar_margin_height 0.0 0.0 ## The margin above and below the tab bar (in pts). The first number ## is the margin between the edge of the OS Window and the tab bar and ## the second number is the margin between the tab bar and the ## contents of the current tab. tab_bar_style fade ## The tab bar style, can be one of: ## ## fade ## Each tab\'s edges fade into the background color (see tab_fade) ## slant ## Tabs look like the tabs in a physical file ## separator ## Tabs are separated by a configurable separator (see tab_separator) ## powerline ## Tabs are shown as a continuous line with "fancy" separators ## (see tab_powerline_style) ## custom ## A user-supplied Python function called draw_tab is loaded from the file ## tab_bar.py in the kitty config directory. For examples of how to ## write such a function, see the functions named draw_tab_with_* in ## kitty\'s source code: kitty/tab_bar.py. See also ## this discussion https://github.com/kovidgoyal/kitty/discussions/4447 ## for examples from kitty users. ## hidden ## The tab bar is hidden. If you use this, you might want to create a ## mapping for the https://sw.kovidgoyal.net/kitty/actions/#select-tab ## action which presents you with a list of tabs and allows for easy ## switching to a tab. tab_bar_align left ## The horizontal alignment of the tab bar, can be one of: left, ## center, or right. tab_bar_min_tabs 2 ## The minimum number of tabs that must exist before the tab bar is ## shown tab_switch_strategy previous ## The algorithm to use when switching to a tab when the current tab ## is closed. The default of previous will switch to the last used ## tab. A value of left will switch to the tab to the left of the ## closed tab. A value of right will switch to the tab to the right of ## the closed tab. A value of last will switch to the right-most tab. tab_fade 0.25 0.5 0.75 1 ## Control how each tab fades into the background when using fade for ## the tab_bar_style. Each number is an alpha (between zero and one) ## that controls how much the corresponding cell fades into the ## background, with zero being no fade and one being full fade. You ## can change the number of cells used by adding/removing entries to ## this list. tab_separator " ┇" ## The separator between tabs in the tab bar when using separator as ## the tab_bar_style. tab_powerline_style angled ## The powerline separator style between tabs in the tab bar when ## using powerline as the tab_bar_style, can be one of: angled, ## slanted, or round. tab_activity_symbol none ## Some text or a unicode symbol to show on the tab if a window in the ## tab that does not have focus has some activity. If you want to use ## leading or trailing spaces surround the text with quotes. See ## tab_title_template for how this is rendered. tab_title_template "{fmt.fg.red}{bell_symbol}{activity_symbol}{fmt.fg.tab}{title}" ## A template to render the tab title. The default just renders the ## title with optional symbols for bell and activity. If you wish to ## include the tab-index as well, use something like: {index}: ## {title}. Useful if you have shortcuts mapped for goto_tab N. If you ## prefer to see the index as a superscript, use {sup.index}. In ## addition you can use {layout_name} for the current layout name, ## {num_windows} for the number of windows in the tab and ## {num_window_groups} for the number of window groups (not counting ## overlay windows) in the tab. Note that formatting is done by ## Python\'s string formatting machinery, so you can use, for instance, ## {layout_name[:2].upper()} to show only the first two letters of the ## layout name, upper-cased. If you want to style the text, you can ## use styling directives, for example: ## {fmt.fg.red}red{fmt.fg.tab}normal{fmt.bg._00FF00}green ## bg{fmt.bg.tab}. Similarly, for bold and italic: ## {fmt.bold}bold{fmt.nobold}normal{fmt.italic}italic{fmt.noitalic}. ## Note that for backward compatibility, if {bell_symbol} or ## {activity_symbol} are not present in the template, they are ## prepended to it. active_tab_title_template none ## Template to use for active tabs, if not specified falls back to ## tab_title_template. xxxxxactive_tab_foreground #000 active_tab_background #eee active_tab_font_style bold-italic inactive_tab_foreground #444 yyyyinactive_tab_background #999 zzzzzinactive_tab_font_style normal ## Tab bar colors and styles tab_bar_background none ## Background color for the tab bar. Defaults to using the terminal ## background color. tab_bar_margin_color none ## Color for the tab bar margin area. Defaults to using the terminal ## background color. '; $subst = "$2\n$1"; $result = preg_replace($re, $subst, $str); echo "The result of the substitution is ".$result;

Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php