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aaronmk
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#!/bin/bash
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aaronmk
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# Expands bash-style {} expressions.
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# See <http://www.gnu.org/software/bash/manual/bash.html#Brace-Expansion>.
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aaronmk
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# Usage: [env expand_braces_debug=1] self <in >out
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aaronmk
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# Filters each line from stdin to stdout.
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# Warning: Due to shell limitations, a blank line will be interpreted as EOF.
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sedEreFlag="$(test "$(uname)" = Darwin && echo E || echo r)"
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sed () { "$(which sed)" -"$sedEreFlag" "$@";}
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echoEach () { local line; for line in "$@"; do echo "$line"; done; }
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replaceRecursive ()
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{
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local sedExpr="$1" str="$2" prevStr
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while true; do
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prevStr="$str"
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str="$(echo "$str"|sed -e "$sedExpr")"
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test "$str" = "$prevStr" && break # done if nothing replaced
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done
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echo "$str"
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}
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debug ()
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{
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local label="$1" str="$2"
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test -n "$expand_braces_debug" && (echo "** $label:"; echo "$str") >&2
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}
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singleQuote="'"
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singleQuoteEsc="'\''"
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CR=$'\r'
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LF=$'\n'
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aaronmk
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nonBracket="[^][]*" # matches non-[] chars
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brackets="($nonBracket\[$nonBracket\])*$nonBracket"
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aaronmk
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while true; do
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read -r # get next line from stdin; strips trailing newlines; -r: raw input
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line="$REPLY"
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test -z "$line" && break # EOF if no line or empty line
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aaronmk
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line="${line//$CR/}" # remove \r
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origLine="$line"
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debug orig "$line"
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line="${line//$singleQuote/$singleQuoteEsc}" # escape single quotes
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line="$(echo "$line"|sed -e "s/[^{,}]+/'&'/g")" # escape non-brace chars
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# Escape commas inside [], which should not be used for {}.
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# Note that '' around "," are closing and opening the escaped string,
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# not the other way around.
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line="$(replaceRecursive "s/(\[$nonBracket)','/\1,/g" "$line")" # innermost
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# Also support one level of nesting, which is the most we currently use.
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line="$(replaceRecursive "s/(\[$brackets)','/\1,/g" "$line")" # 1st outer
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debug escaped "$line"
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debug expanded
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eval echoEach $line # brace-expand $line
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aaronmk
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done
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