A set of Linux Shell scripting little Exercises

# Linux Shell splits strings into groups

result=$ (facter | awk '/ipaddress/&&!/ipaddress_lo/{print $ "$ $} ') array= ($result)

# Determine if a variable exists (not to determine whether it is empty)

If [-Z ${var+x}]; Then echo "Var is unset"; else echo "Var is set to ' $var '"; Fi

# Determine if a variable is empty

If ["$var x" = "x"]; Then echo "Var is empty"; else echo "Var is set to ' $var '"; fiif [-Z $var]; Then echo "Var is empty"; else echo "Var is set to ' $var '"; Fi

#系统变量用后还原

# Definition of IFS: ifs,internal Field Separator

# an Internal Field Separator (IFS) is a environment variable that stores delimiting characters.

# It's 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 b Y the first character of the IFS special variable.

# that's, "$*" 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 was separated by spaces. If IFS is null, the parameters is joined without intervening separators.

oldifs= "$IFS" ifs= "" array= ($result) ifs= "$oldIFS" for I in ${array[@]}; Doecho $idone

# Use Facter to get a set of Key-value

# Facter output has a newline character, you must replace the newline character with a space

# Replace newline characters with spaces to use awk or sed

# awk-v rs= "" ' {gsub ("\ n", "");p rint} '

# ECHO-E "2 \n1" | Sed ': A; n;$!ba;s/\n//g '

result=$ (facter | awk '/ipaddress/&&!/ipaddress_lo/{print "" $ $} ' | Awk-v rs= "" ' {gsub ("\ n", "");p Rint} ') array= ($result) array_length=${#array [@]}

# Output key

for ((i = 0; i < $array _length; i=i+2)); Doecho ${array[$i]}done

# output value

for ((i = 1; i < $array _length; i=i+2)); Doecho ${array[$i]}done

# Output Key-value

for ((i = 0; i < $array _length; i=i+2)); doj= $i +1echo "${array[$i]}-${array[$j]}" done

--end--

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A set of Linux Shell scripting little Exercises