下面用一个简单的shell程序要说明一下。

debian:~/learn/shell#catphonebook

AliceChebba973-555-2015

BarbaraSwingle201-555-9257

LizStachiw212-555-2298

SusanGoldberg201-555-7776

SusanTopple212-555-4932

TonyIannino973-555-1295

StromboliPizza973-555-9478

debian:~/learn/shell#

debian:~/learn/shell#catlu

#Looksomeoneupinthephonebook

grep"$1"phonebook

debian:~/learn/shell#

这是正确的lu程序，下面是运行结果。

debian:~/learn/shell#./lu'SusanT'

SusanTopple212-555-4932

debian:~/learn/shell#./luTony

TonyIannino973-555-1295

debian:~/learn/shell#

如果lu写成①grep$1phonebook或者②grep'$1'phonebook，就会出现下面的错误结果（为什么？）。

①的结果：

debian:~/learn/shell#./luTony//这种情况结果正确

TonyIannino973-555-1295

debian:~/learn/shell#./lu'SusanT'//这种情况结果错误

grep:T:Nosuchfileordirectory

phonebook:SusanGoldberg201-555-7776

phonebook:SusanTopple212-555-4932

debian:~/learn/shell#

②的结果：

debian:~/learn/shell#./luTony//这种情况结果错误

debian:~/learn/shell#./lu'SusanT'//这种情况结果也错误

debian:~/learn/shell#