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alphaniner

Member

From: Ancapistan

Registered: 2010-07-12

Posts: 2,810

[Solved] shopt trouble (bash)

Bash builtin shopt doesn't seem to function when called from within an if block:

#!/bin/bash

if [[ "$1" ]]; then
    eths=($1)
else
    shopt -s extglob
    eths=(/sys/class/net/!(lo))
    shopt -u extglob
fi

printf "%s\n" "${eths[@]}"

Output:

$ ./wtf
./wtf: line 7: syntax error near unexpected token `('
./wtf: line 7: `    eths=(/sys/class/net/!(lo))'
./wtf: line 9: syntax error near unexpected token `fi'
./wtf: line 9: `fi'

Output is the same if the shopt lines are commented out.

OTOH, when shopt is called from without the block:

#!/bin/bash

shopt -s extglob
if [[ "$1" ]]; then
    eths=($1)
else
    eths=(/sys/class/net/!(lo))
fi
shopt -u extglob

printf "%s\n" "${eths[@]}"

I get the expected result:

$ ./wtf
/sys/class/net/net0
/sys/class/net/net0b
/sys/class/net/net1
/sys/class/net/net2
/sys/class/net/net3
/sys/class/net/virbr0
/sys/class/net/virbr0-nic

I didn't see anything in bash(1) suggesting this is expected behaviour, and my google-fu is too weak to craft a useful query.

Edit: Maybe vim is trying to tell me something as the syn highlighting is different without
shopt -s extglob
and within
shopt -s extglob
the block?

Edit: To be clear, this is just a small component of a larger script I use to print network details:

[net0b]
 199.200.1.110
 1000Mb/s
 3.38M / 51.83M

[net1]
 192.168.1.110
 192.168.2.110
 1000Mb/s
 2.27G / 2.15G

[net2]
 192.168.0.110

[net3]
 10.157.4.118
 100Mb/s
 105.10M / 5.47M

[virbr0]
 192.168.122.1

Last edited by alphaniner (2016-07-08 18:03:34)

---

But whether the Constitution really be one thing, or another, this much is certain - that it has either authorized such a government as we have had, or has been powerless to prevent it. In either case, it is unfit to exist.
-Lysander Spooner

edacval

Member

From: .LT

Registered: 2008-10-23

Posts: 98

Re: [Solved] shopt trouble (bash)

From  http://mywiki.wooledge.org/glob :

Because the extglob option changes the way certain characters are parsed, it is necessary to have a newline (not just a semicolon) between the shopt command and any subsequent commands that use extended globs. Likewise, you cannot put shopt -s extglob inside a statement block that uses extended globs, because the block as a whole must be parsed when it's defined; the shopt command won't take effect until the block is evaluated, at which point it's too late. In fact as bash parses the entire statement block before evaluating any of it, you need to set extglob outside of the outermost block.

Last edited by edacval (2016-07-08 18:00:22)

alphaniner

Member

From: Ancapistan

Registered: 2010-07-12

Posts: 2,810

Re: [Solved] shopt trouble (bash)

Thanks!

---

But whether the Constitution really be one thing, or another, this much is certain - that it has either authorized such a government as we have had, or has been powerless to prevent it. In either case, it is unfit to exist.
-Lysander Spooner