linux shell assemble PDF文件

daniel@daniel-mint ~/latex/linux/itext/daniel $ cat asm.sh 
header_start=0
header_len=15

xref_start=$(strings -a -t d $1 | grep -e "\bxref\b" | awk ‘{print $1}‘)
trailer_start=$(strings -a -t d $1 | grep -e "\btrailer\b" | awk ‘{print $1}‘)
#echo $xref_start
#echo $trailer_start

xref_len=$(echo "$trailer_start - $xref_start" | bc)
#echo $xref_len

header_dump=$(echo "$1" | sed -re ‘s/^(.*)\.pdf/asm\_\1\_header\.bin/g‘)
dd if=$1 of=$header_dump bs=1 skip=$header_start count=$header_len

xref_dump=$(echo "$1" | sed -re ‘s/^(.*)\.pdf/asm\_\1\_xref\.bin/g‘)
dd if=$1 of=$xref_dump bs=1 skip=$xref_start count=$xref_len