From: Decare on

Is there any to determine whether a string
is a integer or not? For example,

read s
if [ ... ]; then
do something
else
do another
fi

--
cogito ergo sum!
From: Ivan Shmakov on
>>>>> Decare <decare(a)yeah.net> writes:

> Is there any to determine whether a string is a integer or not? For
> example,

> read s
> if [ ... ]; then

Well, I guess that someone could suggest a way to do so based on
some feature built into modern Shells and that I've didn't
manage to remember as of yet, but here's the way I'd do it:

if echo "$s" | grep -qE '^[[:digit:]]+$' ; then

The 'echo' command may be somewhat unsafe, though it apparently
doesn't affect this particular code fragment.

$ (s=-e ; echo "$s")

$ (s=-n ; echo "$s")
$

> do something
> else
> do another
> fi

--
FSF associate member #7257
From: Janis Papanagnou on
Decare wrote:
> Is there any to determine whether a string
> is a integer or not?

A "modern shell" way (as mentioned upthread) is, e.g.

[[ ${var} == +([0-9]) ]]


Janis

> For example,
>
> read s
> if [ ... ]; then
> do something
> else
> do another
> fi
>
From: Stephane CHAZELAS on
2010-03-13, 06:48(-01), Decare:
>
> Is there any to determine whether a string
> is a integer or not? For example,
>
> read s
> if [ ... ]; then
> do something
> else
> do another
> fi

For negative or positive decimal integers (not supporting 1e6 or
12. or 1,000,000 or +12 or 0x12...):

case $s in
("" | - | *[!0-9-]* | ?*-*) echo no;;
(*) echo yes;;
esac

or:

case ${s#-} in
("" | *[!0-9]*) echo no;;
(*) echo yes;;
esac

--
St├ęphane
From: SM on
2010-03-13, Decare skribis:
>
> Is there any to determine whether a string
> is a integer or not? For example,
>
> read s
> if [ ... ]; then
> do something
> else
> do another
> fi
>

I came across this kind of hack:

is_int() {
printf "%d" $1 > /dev/null 2>&1
return $?
}

read s
if is_int "$s"; then
echo "$s is an integer."
else
echo "$s is not an integer."
fi

--
kasmra
:wq