Using grep with test and without using [[ ]] Post: 303029170

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Top Forums Shell Programming and Scripting Using grep with test and without using [[ ]] Post 303029170 by RudiC on Tuesday 22nd of January 2019 04:58:45 PM

01-22-2019

Registered User

Welcome to the forum.

The "equal-tilde" is explained in man bash's "Compound Commands" paragraph:

Quote:

An additional binary operator, =~, is available, with the same precedence as == and !=. When it is used, the string to the right of the operator is considered an extended regular expression and matched accordingly (as in regex(3)).

You can use your regex (almost) as given in a grep command:

Code:

grep "^[-0-9]\+$" <<<  "$INT"

The + needs to be escaped as grep uses basic regexes by default. For the rest of your request, just replace the [ with test and drop the ] . Please be aware that your script is missing two fi statements. And, reasonable indentation improves readability and understandability of your code.

Code:

if grep "^[-0-9]\+$" <<<  "$INT"
  then  if test "$INT" -eq 0 
          then  echo "INT is zero."
          elif  test "$INT" -lt 0 
            then        echo "INT is negative."
            else        echo "INT is positive."
        fi
  else  echo "No int"
fi

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LEARN ABOUT ULTRIX

regex

regex(3)						     Library Functions Manual							  regex(3)

Name
       re_comp, re_exec - regular expression handler

Syntax
       char *re_comp(s)
       char *s;

       re_exec(s)
       char *s;

Description
       The  subroutine	compiles  a string into an internal form suitable for pattern matching.  The subroutine checks the argument string against
       the last string passed to

       The subroutine returns 0 if the string s was compiled successfully; otherwise a string containing an  error  message  is  returned.  If	is
       passed 0 or a null string, it returns without changing the currently compiled regular expression.

       The  subroutine returns 1 if the string s matches the last compiled regular expression, 0 if the string s failed to match the last compiled
       regular expression, and -1 if the compiled regular expression was invalid (indicating an internal error).

       The strings passed to both and may have trailing or embedded newline characters; they are terminated by	nulls.	 The  regular  expressions
       recognized are described in the manual entry for given the above difference.

Diagnostics
       The subroutine returns -1 for an internal error.

       The subroutine returns one of the following strings if an error occurs:

       No previous regular expression
       Regular expression too long
       unmatched (
       missing ]
       too many () pairs
       unmatched )

See Also
       ed(1), ex(1), egrep(1), fgrep(1), grep(1)

																	  regex(3)

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