#!/bin/bash
# testing the if statement
if date
thenecho "it worked"
fi

#!/bin/bash
#testing multiple commands in the then section
testuser=jiqing9006
if grep $testuser /etc/passwd
thenecho The bash files for user $testuser are:ls -a /home/$testuser/.b*
fi

#!/bin/bash
#testing multiple commands in the then section
testuser=jim
if grep $testuser /etc/passwd
thenecho The bash files for user $testuser are:ls -a /home/$testuser/.b*
elseecho "The user name $testuser does't exist on this system"
fi

#!/bin/bash
#testing multiple commands in the then section
user1=jim
user2=jiqing9006
if grep $user1 /etc/passwd
thenecho The bash files for user $user1 are:ls -a /home/$user1/.b*
elif grep $user2 /etc/passwd
thenecho The bash files for user $user2 are:ls -a /home/$user2/.b*
elseecho "The user name $user1 and $user2 does't exist on this system"
fi

#!/bin/bash
#using numeric test comparisons
val1=10
val2=11
if [ $val1 -gt 5 ]
thenecho "The test value $val1 is greater than 5"
fiif [ $val1 -eq $val2 ]
thenecho "The values are equal"
elseecho "The values are not equal"
fi

#!/bin/bash
#testing string equality
testuser=root
if [ $USER = $testuser ]
thenecho "Welcome $testuser"
fi

#!/bin/bash
#testing string equality
testuser=baduser
if [ $USER != $testuser ]
thenecho "This isn't $testuser"
elseecho "Welcome $testuser"
fi

#!/bin/bash
#mis-using string comparisons
val1=baseball
val2=hockey
val3=book
val4=Book
if [ $val1 \> $val2 ]
thenecho "$val1 is greater than $val2"
elseecho "$val1 is less than $val2"
fi
if [ $val1 \> $val3 ]
thenecho "$val1 is greater than $val3"
elseecho "$val1 is less than $val3"
fi
if [ $val1 \> $val2 ]
thenecho "$val3 is greater than $val4"
elseecho "$val3 is less than $val4"
fi

#!/bin/bash
#testing string length
str1="helloworld"
str2=""
if [ -n $str1 ]
thenecho "str1 is not null"
elseecho "str1 is null"
fiif [ -z $str2 ]
thenecho "str2 is null"
elseecho "str2 is not null"
fi

#!/bin/bash
#look before you leap
if [ -d $HOME ]
thenecho "Your HOME directory exists"cd $HOMEls -l
elseecho "There is a problem with your HOME directory"
fi

#!/bin/bash
# check if a directory exists
if [ -e $HOME ]
thenecho "Your home directory exists"#check if file exists in the directoryif [ -e $HOME/testing ]thenecho "$HOME/tesing exist in the directory"date >>$HOME/testingelseecho "Create a new file"date >$HOME/testingfi
elseecho "Your home directory doesn't exists"
fi

#!/bin/bash
#testing if a file
if [ -e $HOME ]
thenecho "The obj exist,if it is a file?"if [ -f $HOME ]thenecho "Yes,it is a file!"elseecho "No,it is not a file!"if [ -f $HOME/testing ]thenecho "But $HOME/testing is a file!"elseecho "$HOME/testing is not a file too!"fifi
elseecho "The obj doesn't exist"
fi

#!/bin/bash
#testing if can read a file
pwfile=/etc/shadow
#first,check if it is a file
if [ -f $pwfile ]
then#now test if you can read itif [ -r $pwfile ]thentail $pwfileelseecho "sorry,the file can be read."fi
elseecho "sorry,it is not a file."
fi

#!/bin/bash
#testing a file is empty
file=testfile
touch $fileif [ -s $file ]
then  echo "The $file exists and has data in it"
elseecho "The $file doesn't exist or is empty"
fidate >$file
if [ -s $file ]
thenecho "The $file exists and has data in it"
elseecho "The $file doesn't exist or is empty"
fi

#!/bin/bash
#checking if a file if writeable
logfile=$HOME/logtest
touch $logfile
chmod u-w $logfile
now=`date +%Y%m%d-%H%M`if [ -w $logfile ]
thenecho "The program ran at:$now">>$logfileecho "The first attempt succeeded"
elseecho "The first attempt failed"
fichmod u+w $logfile
if [ -w $logfile ]
thenecho "The program ran at:$now">>$logfileecho "The second attempt succeeded"
elseecho "The second attempt failed"
fi

#!/bin/bash
#testing file dates
if [ ./test1 -nt ./test10 ]
thenecho "The test1 file is newer than test10"
elseecho "The test10 file is newer than test1"
fiif [ ./test1 -ot ./test10 ]
thenecho "The test1 file is older than test10"
elseecho "The test10 file is older than test1"
fi

#!/bin/bash
#testing compound comparisons
if [ -d $HOME ] && [ -x $HOME/testing ]
thenecho "The file exists and you can execute it"
elseecho "You can't execute the file"
fi

#!/bin/bash
#using double parenthesis
val1=10
if (($val1**2>90))
then((val2 =$val1**2))echo "The square of $val1 is $val2"
fi

#!/bin/bash
# using pattern matching
if [[ $USER==r* ]]
thenecho "Hello $USER"
elseecho "Sorry,I don't know you"
fi

#!/bin/bash
#using the case command
case $USER in
rich | barbara)echo "Welcome,$USER"ehco "Please enjoy your visit";;
testing)echo "Special testing account";;
jessica)echo "Don't forget to log off when you're done";;
root)echo "Welcome,Manager";;
*)echo "Sorry,you're not allowed here";;
esac

---

本文转自TBHacker博客园博客，原文链接：http://www.cnblogs.com/jiqing9006/p/3198346.html，如需转载请自行联系原作者