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1
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#!/bin/sh -e
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2
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# Runs a stream command on a file
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3
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# Usage: [preserve_mtime=1] self file command
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4
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5
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file="$1"
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6
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shift
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7
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8
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test "$#" -ge 1 || exit 0 # no command to run
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9
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10
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temp="$(tempfile)"
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11
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onExit () { rm -f "$temp"; }
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12
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trap onExit EXIT
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13
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14
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"$@" <"$file" >"$temp" # exits on error so file not updated
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15
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diff --brief "$file" "$temp" >/dev/null && exit # don't update file if no change
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16
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# --brief: avoid scanning the entire file for large files
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17
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if test "$preserve_mtime"; then touch -r "$file" "$temp"; fi
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18
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case "$(uname)" in Linux) chmod --reference="$file" "$temp";; esac
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19
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mv "$temp" "$file"
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