条件选择
case
用
case $variable-name in
pattern1)
command1
...
....
commandN
;;
pattern2)
command1
...
....
commandN
;;
patternN)
command1
...
....
commandN
;;
*)
esac
# 或者
case $variable-name in
pattern1|pattern2|pattern3)
command1
...
....
commandN
;;
pattern4|pattern5|pattern6)
command1
...
....
commandN
;;
pattern7|pattern8|patternN)
command1
...
....
commandN
;;
*)
esac
使用$variable-name 与模式进行比较，直到找到匹配项为止。*) 是默认值，如果没有找到匹配项则执行。该模式可以包含通配符。您必须包括 ;; 在每个命令的末尾
#!/bin/bash
# if no command line arg given
# set rental to Unknown
if [ -z $1 ]
then
rental="*** Unknown vehicle ***"
elif [ -n $1 ]
then
# otherwise make first arg as a rental
rental=$1
fi
# use case statement to make decision for rental
case $rental in
"car") echo "For $rental rental is Rs.20 per k/m.";;
"van") echo "For $rental rental is Rs.10 per k/m.";;
"jeep") echo "For $rental rental is Rs.5 per k/m.";;
"bicycle") echo "For $rental rental 20 paisa per k/m.";;
"enfield") echo "For $rental rental Rs.3 per k/m.";;
"thunderbird") echo "For $rental rental Rs.5 per k/m.";;
*) echo "Sorry, I can not get a $rental rental for you!";;
esac
*（默认选项
#!/bin/bash
NOW=$(date +"%a")
case $NOW in
Mon)
echo "Full backup";;
Tue|Wed|Thu|Fri)
echo "Partial backup";;
Sat|Sun)
echo "No backup";;
*) ;;
esac
以下
#!/bin/bash
OPT=$1 # option
FILE=$2 # filename
# test -e and -E command line args matching
case $OPT in
-e|-E)
echo "Editing $2 file..."
# make sure filename is passed else an error displayed
[ -z $FILE ] && { echo "File name missing"; exit 1; } || vi $FILE
;;
-c|-C)
echo "Displaying $2 file..."
[ -z $FILE ] && { echo "File name missing"; exit 1; } || cat $FILE
;;
-d|-D)
echo "Today is $(date)"
;;
*)
echo "Bad argument!"
echo "Usage: $0 -ecd filename"
echo " -e file : Edit file."
echo " -c file : Display file."
echo " -d : Display current date and time."
;;
esac
最后的示例中，我们可以将多种备份选择整合到某个单一脚本中：
#!/bin/bash
# A shell script to backup mysql, webserver and files to tape
opt=$1
case $opt in
sql)
echo "Running mysql backup using mysqldump tool..."
;;
sync)
echo "Running backup using rsync tool..."
;;
tar)
echo "Running tape backup using tar tool..."
;;
*)
echo "Backup shell script utility"
echo "Usage: $0 {sql|sync|tar}"
echo " sql : Run mySQL backup utility."
echo " sync : Run web server backup utility."
echo " tar : Run tape backup utility." ;;
esac
chmod +x allinonebackup.sh
# run sql backup
./allinonebackup.sh sql
# Dump file system using tape device
./allinonebackup.sh tar
# however, the following will fail as patterns are case sensitive
# you must use command line argument tar and not TAR, Tar, TaR etc.
./allinonebackup.sh TAR
大小写敏感
根据大写和小写字母的不同用法，单词的含义可能会有所不同。
./allinonebackup.sh tar
但是，以下示例将不起作用，因为模式区分大小写。您必须使用命令行参数
./allinonebackup.sh TAR
转化为小写
您可以使用
echo "TeSt" | tr '[:upper:]' '[:lower:]'
var="TesT"
tr '[:upper:]' '[:lower:]' <<<"$var"
您可以按以下方式更新脚本：
#!/bin/bash
# A shell script to backup mysql, webserver and files to tape
# allinonebackup.sh version 2.0
# -------------------------------------------------------
# covert all passed arguments to lowercase using
# tr command and here strings
opt=$( tr '[:upper:]' '[:lower:]' <<<"$1" )
case $opt in
sql)
echo "Running mysql backup using mysqldump tool..."
;;
sync)
echo "Running backup using rsync tool..."
;;
tar)
echo "Running tape backup using tar tool..."
;;
*)
echo "Backup shell script utility"
echo "Usage: $0 {sql|sync|tar}"
echo " sql : Run mySQL backup utility."
echo " sync : Run web server backup utility."
echo " tar : Run tape backup utility." ;;
esac
使用正则表达式
大小写命令模式支持正则表达式，这些正则表达式提供了一种简洁而灵活的方式来标识单词或字符模式。例如，您可以使用以下语法匹配
[Tt][Aa][Rr]
上面称为方括号表达式。它与括号中包含的单个字符匹配。
# A shell script to backup mysql, webserver and files to tape
opt=$1
#########################################################
# Use regex to match all command line arguments #
# [Tt][Aa][Rr] matches "tar", "TAR", "taR", "TaR", etc #
# [Ss][Qq][Ll] matches "sql", "SQL", "SQl", "SqL", etc #
#########################################################
case $opt in
[Ss][Qq][Ll])
echo "Running mysql backup using mysqldump tool..."
;;
[Ss][Yy][Nn][Cc])
echo "Running backup using rsync tool..."
;;
[Tt][Aa][Rr])
echo "Running tape backup using tar tool..."
;;
*)
echo "Backup shell script utility"
echo "Usage: $0 {sql|sync|tar}"
echo " sql : Run mySQL backup utility."
echo " sync : Run web server backup utility."
echo " tar : Run tape backup utilty." ;;
esac
启用大小写不敏感
# 启用
shopt -s nocasematch
# 关闭
shopt -u nocasematch
这是相同的更新版本：
# A shell script to backup mysql, webserver and files to tape
opt=$1
# Turn on a case-insensitive matching (-s set nocasematch)
shopt -s nocasematch
case $opt in
sql)
echo "Running mysql backup using mysqldump tool..."
;;
sync)
echo "Running backup using rsync tool..."
;;
tar)
echo "Running tape backup using tar tool..."
;;
*)
echo "Backup shell script utility"
echo "Usage: $0 {sql|sync|tar}"
echo " sql : Run mySQL backup utility."
echo " sync : Run web server backup utility."
echo " tar : Run tape backup utilty." ;;
esac
# Turn off a case-insensitive matching (-u unset nocasematch)
shopt -u nocasematch