Regex to validate parameter for sleep Post: 303025524

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Top Forums Shell Programming and Scripting Regex to validate parameter for sleep Post 303025524 by Ralph on Monday 5th of November 2018 08:10:03 AM

11-05-2018

Registered User

Regex to validate parameter for sleep

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:

Code:

if ! [[ $1 =~ ^\+?\.?[0-9]+\.?[0-9]*$ ]] || [[ $1 =~ ^[\+-]?0?\.?0*$ ]] && ! [[ $1 =~ ^\.*$ ]

but it looks even more contrived now.

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.)

------ Post updated at 01:10 PM ------

OMG. There's a ] missing at the end.

Ralph

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LEARN ABOUT SUNOS

regcmp

regcmp(1)							   User Commands							 regcmp(1)

NAME

       regcmp - regular expression compile

SYNOPSIS

       regcmp [-] filename...

DESCRIPTION

       The regcmp command performs a function similar to regcmp and, in most cases, precludes the need for calling regcmp from C programs. Bypass-
       ing regcmp saves on both execution time and program size. The command regcmp compiles the regular expressions in filename  and  places  the
       output in filename.i.

OPTIONS

       -	If  the - option is used, the output is placed in filename.c. The format of entries in filename is a name (C variable) followed by
		one or more blanks followed by one or more regular expressions enclosed in double quotes. The output of regcmp is C  source  code.
		Compiled  regular  expressions	are  represented  as extern char vectors. filename.i files may thus be #included in C programs, or
		filename.c files may be compiled and later loaded. In the C program that uses the regcmp output, regex(abc,line) applies the regu-
		lar expression named abc to line. Diagnostics are self-explanatory.

EXAMPLES

       Example 1: Examples of the regcmp command.

       name	"([A-Za-z][A-Za-z0-9_]*)$0"

       telno	"({0,1}([2-9][01][1-9])$0){0,1} *"

		"([2-9][0-9]{2})$1[ -]{0,1}"

		"([0-9]{4})$2"

       The three arguments to telno shown above must all be entered on one line.

       In the C program that uses the regcmp output,

	    regex(telno, line, area, exch, rest)
       applies the regular expression named telno to line.

ENVIRONMENT VARIABLES

       A general description of the usage of the LC_* environmental variables can be found in environ(5).

       LC_CTYPE        Determines  how	regcmp	handles  characters. When LC_CTYPE is set to a valid value, regcmp can display and handle text and
		       filenames containing valid characters for that locale.

       LC_MESSAGES     Determines how diagnostic and informative messages are presented. This includes the language and style of the messages, and
		       the  correct form of affirmative and negative responses.  In the "C" locale, the messages are presented in the default form
		       found in the program itself (in most cases, U.S. English).

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWtoo			   |
       +-----------------------------+-----------------------------+
       |CSI			     |Enabled			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       regcmp(3C), attributes(5), environ(5)

SunOS 5.10							    Dec 20 1996 							 regcmp(1)