[root@blog ~ 14:05:42]$sed 's/g/dddd/' <<< "ghhhg"
ddddhhhg
[root@blog ~ 14:06:13]$
[root@blog ~ 14:07:21]$var=hello
[root@blog ~ 14:07:30]$sed 's/e/dddd/' <<< "$var"
hddddllo
[root@blog ~ 14:07:43]$
[root@blog ~ 14:07:43]$cat
112
112
输入 ＂ctrl +d ＂,结束输入
[root@blog ~ 14:08:18]$cat <<-eof
> sidid
> eof
sidid
[root@blog ~ 14:08:31]$cat > /tmp/cat.txt <<-eof
> cat disi
> cat idi
> eof
[root@blog ~ 14:08:52]$cat /tmp/cat.txt
cat disi
cat idi
[root@blog ~ 14:08:57]$