I'm trying to use a regular expression to validate a value for sleep entered by the user. The test should fail all negative values and 0 but let pass all combinations of + . and digits that would amount to a valid parameter for sleep.
Examples for valid: 1, 1.5, .5, 0.5, +1, +.5, +1.3 etc.
Examples for invalid: 0, .0, 0., 0.0, +0, +.0, +0, +0.0 etc. and any string starting with a -
I wrote a small program to test the regular expressions I'm using now - two expressions combined in a test statement. While looking a bit contrived they almost do the job except that strings like .1.1 still pass the test as valid.
Can someone help me take the final step?
Code:
#!/bin/bash
if [ $# -gt 0 ] ; then # user entered parameter for sleep
# check fails if it's not a positive floating point number
if ! [[ $1 =~ ^\+?\.?[0-9]+\.?[0-9]*$ ]] || [[ $1 =~ ^[\+-]?0?\.?0*$ ]]; then
echo invalid value for sleep: $1
else
echo valid: $1
fi
fi
Thanks.
------ Post updated at 01:08 PM ------
I found a solution by adding an && clause to the if condition:
Is there a way to solve the problem within one regular expression? Or something much shorter? (I'm not overly familiar with regular expressions and I expect an expert to come up easily with something shorter, humiliatingly shorter.)
sed -r '/-/bW; /[1-9]/ {s/$/\tOK/; b}; :W; s/$/\tWRONG/' file
1 OK
1.5 OK
.5 OK
0.5 OK
+1 OK
.50 OK
0.5000 OK
+100 OK
+.5 OK
+1.3 OK
-1 WRONG
-.5 WRONG
-1.3 WRONG
.0 WRONG
0. WRONG
0.0 WRONG
+0 WRONG
+.0 WRONG
+0 WRONG
+0.0 WRONG
I'm impressed (though after running the code I think the then and else sections should be reversed - see below.)
I admit I'll have to spend a day with sed one of these days and I will, but just assuming all is well - and it looks like it is - what's the exit status of sed used by if here?
According to sed documentation sed returns 0 on successful completion and 1 if it encounters an invalid command, invalid syntax. The latter doesn't seem to be the case here.
In your code it looks like sed returns 0 for a valid value and 1 for an invalid one.
With tplus being (then/else reversed and echo $? added by me):
Code:
if sed -r '/[^0-9+.]|([.]).*\1/q1; /[1-9]/q0; q1' <<< $1
then echo exit status: $?; echo valid: $1
else
echo exit status: $?; echo invalid: $1
fi
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