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1.$ [ -f /tmp/test.txt ] || > /tmp/test.txt
1.$ echo $?; echo $!; echo $$
1.¥var=`grep “upe” notes.txt 3>&2 2>&1 1>&3`; echo $var
2.$ df | sed -n 's/.* \([0-9][0-9]*\)%.*/\1/p'
3.$ while who | grep “^upe” > /dev/null; do
> sleep 60
> done; echo “the cat’s away…”
4.$ set `who | cut –c1-8 | sort -u`; for i; do
> echo “Dear $i” | cat – form_letter | lpr
> done;
说明各行命令的功能和含义?好了好久都找不到,麻烦各位看看了! |
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