Command works when pasted at command line but not as bash script

neild · 09-20-2012, 03:25 PM

I want to run the following bash command at startup.

MAC_ADDR=$(ifconfig eth0 | sed -n 's/.*HWaddr $[a-f0-9:]*$.*/\1/p')
IP=($(curl http://169.254.169.254/latest/meta-data/network/interfaces/macs/$MAC_ADDR/local-ipv4s))
for ip in ${IP[@]:1}; do
echo "Adding IP: $ip"
ip addr add dev eth0 $ip/24
done

I have copied the command from the website silkapp.com.

Basically it gets the secondary internal IP addresses allocated to an Amazon EC2 instance from some remote metadata and adds the IPs to eth0 on the machine.

It works fine when pasted into the command line.

However, if I paste it into /path/script.sh and run:
sh /path/script.sh

I get:

Syntax error: "(" unexpected

How do I get the script to run correctly?

I know pretty much nothing about bash scripts and I imagine this is obvious to some of you, but I am stumped.

Any help would be sincerely appreciated.

chrism01 · 09-20-2012, 08:46 PM

Could be a pasting issue.
Sometimes when pasting into eg vi, a wrapped line like that 'IP=..' will end up with a (invisible) newline char in the middle.
Its an interaction between vi and the clipboard/mouse.
Just go into he editor and make sure each cmd line has no newline char eg by cursoring along the line, it will stop at the newline char,

Habitual · 09-20-2012, 09:54 PM

Quote:

Originally Posted by neild

I want to run the following bash command at startup.

MAC_ADDR=$(ifconfig eth0 | sed -n 's/.*HWaddr $[a-f0-9:]*$.*/\1/p')
IP=($(curl http://169.254.169.254/latest/meta-data/network/interfaces/macs/$MAC_ADDR/local-ipv4s))
for ip in ${IP[@]:1}; do
echo "Adding IP: $ip"
ip addr add dev eth0 $ip/24
done

Might help is code tags were used.

Code:

MAC_ADDR=$(ifconfig eth0 | sed -n 's/.*HWaddr \([a-f0-9:]*\).*/\1/p')
IP=($(curl http://169.254.169.254/latest/meta-data/network/interfaces/macs/$MAC_ADDR/local-ipv4s))
for ip in ${IP[@]:1}; do
    echo "Adding IP: $ip"
    ip addr add dev eth0 $ip/24
done

Quote:

Originally Posted by neild

I have copied the command from the website silkapp.com.

depending on how the original code was rendered on your browser it may have some 'extra' stuff in the pasted clipboard contents.

What does

Code:

curl http://169.254.169.254/latest/meta-data/network/interfaces/macs/$MAC_ADDR/local-ipv4s

in a terminal kick out on this instance?

firstfire · 09-20-2012, 11:30 PM

Hi.

The problem is that POSIX conformable shells (like /bin/sh -> dash on Debian-like systems) lack support for arrays. When you type these commands in command line, you actually use bash, an enhanced shell. Try to run your script as follows:

Code:

bash ./yourscript.sh

..And welcome to LQ!

Zero Angel · 09-21-2012, 12:33 AM

Wouldnt

Code:

#!/bin/bash

on the first line do the same thing?

pan64 · 09-21-2012, 12:59 AM

no, if you specify the shell (like: sh <script>) the shebang will not be used

neild · 09-21-2012, 06:03 AM

Thanks firstfire that is perfect.

Code:

bash ./yourscript.sh

makes the script work as expected. I didn't realise arrays were an additional feature of bash

Quote:

Might help is code tags were used.

Thanks, will bear in mind next time.

If anyone is interested

Code:

curl http://169.254.169.254/latest/meta-data/network/interfaces/macs/$MAC_ADDR/local-ipv4s

returns a line-break delimited list of IP addresses such as:

Code:

10.0.0.1
10.0.0.2
10.0.0.3
10.0.0.4

Quote:

welcome to LQ!

Thanks, sorry I am using first post to ask for help rather than help out.

David the H. · 09-23-2012, 07:30 AM

Quote:

Originally Posted by pan64

no, if you specify the shell (like: sh <script>) the shebang will not be used

Zero Angel almost certainly means the opposite. That is, if the OP ensures that the first line is #!/bin/bash(and not #!/bin/sh or some other executable), then the script will work properly when executed directly. The shebang controls which interpreter is used when the script file is executed as a stand-alone command, ignoring the system default.

In other words, there's no need to explicitly invoke a shell if you code the script properly.

See these links for this and other common scripting mistakes:

http://wiki.bash-hackers.org/scripting/newbie_traps
http://mywiki.wooledge.org/BashPitfalls
http://mywiki.wooledge.org/BashFAQ