一组Linux Shell Scripting小练习
# 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$2c...", where c is the firstchar‐acter of the value of the IFS variable.
# If IFS is unset, the parameters are separated by spaces.If IFS is null, the parameters are joined without intervening separators.
oldIFS="$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--
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