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#!/bin/sh |
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# |
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# Redirect stdin, stdout, stderr of a daemon to /dev/pts/# |
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# |
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################################################################################################################# |
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# Ref: stdio buffering: http://www.pixelbeat.org/programming/stdio_buffering/ |
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# Default Buffering modes: |
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# stdin -> is always buffered |
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# stderr -> is always unbuffered |
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# if stdout is a terminal then buffering is automatically set to line buffered, else it is set to buffered |
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################################################################################################################# |
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# Therefore if we set stdout, stderr unbuffered by setvbuf(), we don't need flush (-f) feature. |
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# However buffered mode stdio is more efficient. |
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################################################################################################################# |
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if [ "$2" = "" ]; then |
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echo "Usage: $0 PID /path/to/pts" |
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echo "Example: $0 \`pidof Daemon\` /dev/pts/1" |
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echo " $0 \`pidof Daemon\` \`tty\`" |
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exit 0 |
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fi |
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SLEEP_DURATION=5 |
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GDB=${GDB:-gdb} |
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if ${GDB} --version > /dev/null 2>&1; then |
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true |
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else |
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echo "Unable to find gdb." |
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fi |
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pid=$1 |
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dst=$2 |
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# -f : flushes all open output streams to avoid buffered IO |
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if [ "${2}" = "-f" ]; then |
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( |
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echo "attach $pid" |
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echo 'call fflush(0)' |
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echo 'detach' |
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echo 'quit' |
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sleep 5 |
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) | ${GDB} -q -x - |
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else |
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( |
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echo "attach $pid" |
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echo 'call open("'$dst'", 66, 0666)' |
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#echo 'call dup2($1,0)' # stdin |
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echo 'call dup2($1,1)' # stdout, $1 derived from previous open() by gdb |
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echo 'call dup2($1,2)' # stderr |
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# NOTE: setvbuf cause SIGSEGV in some situation, |
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# uncomment them if you needed. |
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#echo 'p setvbuf(stdout, 0, 2, 0)' #set _IONBF unbuffered |
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#echo 'p setvbuf(stderr, 0, 2, 0)' #set _IONBF unbuffered |
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echo 'call close($1)' |
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echo 'detach' |
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echo 'quit' |
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sleep $SLEEP_DURATION |
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) | ${GDB} -q -x - |
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fi |
