Why does my bash function handle arguments as a string? - macos

Question

I am attempting to gather my ip address and subnet bits (such as 192.168.2.17/24) to pass to fing along with a name to scan a network and create a set of output files. I wrote a working script that takes in the address/len and a job name. I ultimately want to be able to extend the shell script automatically pull the address/len so that I only need to enter the job name. I'm using a Mac, if that helps.
fing.sh (This works!)
#Create a fing profile and scan
mkdir $2
fing -n $1 -r 3 -d false --session $2/persist.fing \
-o table,html,$2/fing.html -o table,csv,$2/fing.csv \
-o table,xml,$2/fing.xml -o table,json,$2/fing.json
test.sh
#!/bin/bash
#Variables
ipaddr=ip
hexmask=netmask
testmask=255.255.252.0
#thing=0
The ip and netmask functions work; at least they seem to.
#Functions
ip()
{
ifconfig | grep "inet " | grep -v 127.0.0.1 | awk '{print $2}'
}
netmask()
{
ifconfig | grep "inet " | grep -v 127.0.0.1 | awk '{print $4}'
}
The functions, mask2cidr and hex2decip to work as individual scripts.
mask2cidr() {
#Source:
#http://www.linuxquestions.org/questions/programming-9/bash-cidr-calculator-646701/#post3173472
#Convert dotted decimal subnet mask to cidr format
nbits=0
IFS=.
for dec in $1 ; do
case $dec in
255) let nbits+=8;;
254) let nbits+=7;;
252) let nbits+=6;;
248) let nbits+=5;;
240) let nbits+=4;;
224) let nbits+=3;;
192) let nbits+=2;;
128) let nbits+=1;;
0);;
*) echo "Error: $dec is not recognised"; exit 1
esac
done
echo "$nbits"
}
hex2decip()
{
#Source:
#https://forums.freebsd.org/threads/ifconfig-display-non-hex-netmasks.2834/#post-86216
#Converts hex formatted subnet to dotted decimal format
if [ ! "$1" ] ; then
echo
echo "$MyName - converts an IP address in hexadecimal to dotted decimal"
echo "Usage: $MyName <hex_address>"
echo
exit 1
fi
echo $1 | sed 's/0x// ; s/../& /g' | tr [:lower:] [:upper:] | while read B1 B2 B3 B4 ; do
echo "ibase=16;$B1;$B2;$B3;$B4" | bc | tr '\n' . | sed 's/\.$//'
done
}
ipaddr and hexmask output as expected
${ipaddr}
${hexmask}
For hex2decip, hexmask seems to pass "netmask" instead of the result of the netmask function.
hex2decip $hexmask
exit 0
./test.sh OUTPUT
10.0.180.14
0xffffff00
(standard_in) 1: illegal character: N
(standard_in) 1: illegal character: T
(standard_in) 1: illegal character: M
(standard_in) 1: illegal character: S
(standard_in) 1: illegal character: K

Answer 1

hexmask=netmask
Sets the shell variable hexmask to the string netmask. That's just how the shell works.
If you want the result of calling the shell function netmask, you need to use command substitution:
hexmask=$(netmask)
(after first defining the netmask function, of course.)
By the way,
ipaddr=ip
testmask=255.255.252.0
work the same way. ipaddr is set to the string ip and testmask to the string 255.255.252.0.