一组Linux Shell Scripting小练习

zxcvb12

　　# Linux shell将字符串分割成数组
result=$(facter | awk '/ipaddress/ && !/ipaddress_lo/ {print $1 " " $3}')　　
array=($result)
　　# 判断一个变量是否存在（不是判断是否为空）
if [ -z ${var+x} ]; then echo "var is unset"; else echo "var is set to '$var'"; fi　　# 判断一个变量是否为空
if [ "$var x" = " x" ]; then echo "var is empty"; else echo "var is set to '$var'"; fi　　
if [ -z $var ]; then echo "var is empty"; else echo "var is set to '$var'"; fi
　　#系统变量用后还原
　　# 关于IFS的定义：IFS,Internal Field Separator
　　# An Internal Field Separator (IFS) is an environment variable that stores delimiting characters.
　　# It is the default delimiter string used by a running shell environment.
　　# "$*" expands as "$1c$2c$3", where c is the first character of IFS
　　# When the expansion occurs within double quotes, it expands to a single word with the value of each parameter separated by the first character of the IFS special variable.
　　# That is, "$*" is equivalent to "$1c$2c...", where c is the first  char‐acter of the value of the IFS variable.
　　# If IFS is unset, the parameters are separated by spaces.  If IFS is null, the parameters are joined without intervening separators.
oldIFS="$IFS"　　
IFS=" "
　　
array=($result)
　　
IFS="$oldIFS"
　　
for i in ${array[@]}; do
　　
echo $i
　　
done
　　# 使用facter获取一组key-value
　　# facter的输出有换行符，必须把换行符替换成空格
　　# 将换行符替换成空格可以使用awk或sed
　　# awk -v RS="" '{gsub("\n"," ");print}'
　　# echo -e "2 \n1" | sed ':a;N;$!ba;s/\n/ /g'
result=$(facter | awk '/ipaddress/ && !/ipaddress_lo/ {print $1 " " $3}' | awk -v RS="" '{gsub("\n"," ");print}')　　
array=($result)
　　
array_length=${#array[@]}
　　# 输出key
for (( i = 0; i < $array_length; i=i+2 )); do　　echo ${array[$i]}
　　
done
　　# 输出value
for (( i = 1; i < $array_length; i=i+2 )); do　　echo ${array[$i]}
　　
done
　　# 输出key-value
for (( i = 0; i < $array_length; i=i+2 )); do　　j=$i+1
　　echo "${array[$i]} - ${array[$j]}"
　　
done
　　--end--