请教个cat命令的有关问题

请问个cat命令的问题
cat ${cfgfile} | sed -e /filename=system.img/d -e /filename=yaffs2_gnu_system.img/d -e s/size=734003200/size=${rootfs_size}/ -e s/size=471859200/size=${rootfs_size}/ -e s/filename=flashboot.img/filename=boot.img/ > flash.cfg;

请问这句命令的作用是？

请教各位大侠了



[解决办法]
大概是这样,打开${cfgfile}这个变量指向的文件，然后替换里面的一些字符项，然后再写入到flash.cfg中；
[解决办法]

Assembly code

[freebsd:~/shcode ]$cat temp.txt filename=system.imgfilename=yaffs2_gnu_system.imgsize=734003200size=471859200filename=flashboot.img[freebsd:~/shcode ]$cat sh901.shcfgfile=temp.txtrootfs_size=11111cat ${cfgfile} | sed -e /filename=system.img/d -e /filename=yaffs2_gnu_system.img/d -e s/size=734003200/size=${rootfs_size}/ -e s/size=471859200/size=${rootfs_size}/ -e s/filename=flashboot.img/filename=boot.img/ > flash.cfG[freebsd:~/shcode ]$chmod u+x sh901.sh[freebsd:~/shcode ]$./sh901.sh[freebsd:~/shcode ]$lsflash.cfG    sh900.sh    sh901.sh    temp.sh        temp.txt[freebsd:~/shcode ]$cat flash.cfG size=11111size=11111filename=boot.img
[解决办法]
自己新建个文件试一下就知道了：

Assembly code
[freebsd:~/shcode ]$cat temp.txt filename=system.img aafilename=yaffs2_gnu_system.img aasize=734003200size=471859200filename=flashboot.img  aa[freebsd:~/shcode ]$cat sh901.sh cfgfile=temp.txtrootfs_size=11111cat ${cfgfile} | sed -e /filename=system.img/d -e /filename=yaffs2_gnu_system.img/d -e s/size=734003200/size=${rootfs_size}/ -e s/size=471859200/size=${rootfs_size}/ -e s/filename=flashboot.img/filename=boot.img/ > flash.cfG[freebsd:~/shcode ]$./sh901.sh[freebsd:~/shcode ]$cat flash.cfGsize=11111size=11111filename=boot.img  aa