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kunalkakade
140 lines
4.3 KiB
Markdown
140 lines
4.3 KiB
Markdown
# String functions
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The `string.*` commands manipulate and inspect text from within the
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configuration file.
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They are pure functions with no side effects, so they can be nested freely and
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are safe to call over RPC.
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Every argument is converted to its string representation before use, which means
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numbers can be passed where text is expected.
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Commands that count characters, such as `string.length` and `string.substr`, count
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utf-8 characters rather than bytes.
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## string.length
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# string.length = «text»
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string.length = "héllo" # 5
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Returns the number of utf-8 characters in the text.
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## string.equals
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# string.equals = «text», «other»[, ...]
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string.equals = (d.name), "first.iso", "second.iso"
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Returns `1` if the first argument equals any of the following arguments,
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otherwise `0`.
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## string.starts_with, string.ends_with
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# string.starts_with = «text», «prefix»[, ...]
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# string.ends_with = «text», «tail»[, ...]
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string.starts_with = (t.url), "http://", "https://"
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string.ends_with = (d.name), ".iso"
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Returns `1` if the text begins, or ends, with any of the given prefixes or
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tails.
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## string.contains, string.contains_i
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# string.contains = «haystack», «needle»[, ...]
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# string.contains_i = «haystack», «needle»[, ...]
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string.contains = (t.url), "retracker.local"
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string.contains_i = (t.url), "RETRACKER.local"
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Returns `1` if the haystack contains any of the needles.
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The `_i` variant compares case-insensitively, and only handles ascii.
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## string.substr
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# string.substr = «text»[, «position»[, «count»[, «default»]]]
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string.substr = "abcdef", 2, 3 # "cde"
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string.substr = "abcdef", -2 # "ef"
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string.substr = "abcdef", 10, 1, "?" # "?"
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Extracts a part of the text, starting at `position` and spanning `count`
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characters.
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The position defaults to the start of the text, and the count to the rest of it.
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A negative position is relative to the end of the text.
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If the position falls outside the text, the default value is returned instead,
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which is the empty string unless given.
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## string.split
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# string.split = «text», «delimiter»
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string.split = "a.b.c", "." # {"a", "b", "c"}
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string.split = "abc", "" # {"a", "b", "c"}
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Splits the text into a list, keeping empty fields.
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An empty delimiter splits the text into its utf-8 characters.
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## string.join
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# string.join = «delimiter»[, «object»[, ...]]
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string.join = "-", (string.split, "a.b.c", ".") # "a-b-c"
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Concatenates the objects, inserting the delimiter between them.
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Lists are flattened, so the result of `string.split` can be joined back
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together.
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## string.lpad, string.rpad
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# string.lpad = «text», «length»[, «padding»]
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# string.rpad = «text», «length»[, «padding»]
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string.lpad = 7, 3, 0 # "007"
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string.rpad = "a", 3 # "a "
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Pads the text at the start, or the end, until it is `length` characters long.
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The padding defaults to a single space and is repeated as needed.
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Text that is already long enough is returned unchanged.
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## string.strip, string.lstrip, string.rstrip
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# string.strip = «text»[, «strippable»[, ...]]
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# string.lstrip = «text»[, «head»[, ...]]
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# string.rstrip = «text»[, «tail»[, ...]]
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string.strip = " padded " # "padded"
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string.strip = "//path//", "/" # "path"
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Removes characters from both ends of the text, or from only the start or the
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end.
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The arguments after the text form a set of utf-8 characters to remove.
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Without them, whitespace is removed.
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## string.map
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# string.map = «text», {«old», «new»}[, ...]
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string.map = (d.state), {0, "stopped"}, {1, "started"}
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Returns the replacement of the first pair whose `old` value equals the whole
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text.
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If no pair matches, the text is returned unchanged.
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## string.replace
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# string.replace = «text», {«old», «new»}[, ...]
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string.replace = "a-b-c", {"-", "+"} # "a+b+c"
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Replaces every occurrence of `old` with `new`.
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The pairs are applied in order, so a later pair operates on the result of the
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earlier ones.
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## Example: dropping unwanted trackers
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The following disables every tracker that points at `retracker.local` as soon as
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a download is inserted.
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method.set_key = event.download.inserted, drop_retracker, \
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((t.multicall, default, "branch=(string.contains,(t.url),retracker.local),((t.disable))"))
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