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Full Discussion: test for a blank string
Top Forums Shell Programming and Scripting test for a blank string Post 302596800 by Skrynesaver on Wednesday 8th of February 2012 10:00:09 AM
Old 02-08-2012
The test above =~ is pure Perl, you need to use either Perl the grep command to perform your regex chack as regex is not available in the shell.
thus
Code:
$ VALUE=
$ echo $VALUE | grep -E '^[:space]*$'

$ echo $?
0
$  VALUE=1
$ echo $VALUE | grep -E '^[:space]*$'
$ echo $?
1

OR
Code:
$ echo $VALUE
1
$ perl -e 'print "BAD_USER\n" if $ARGV[0] =~/^\s*$/' $VALUE
$ VALUE=
$ echo $VALUE | perl -e 'print "BAD_USER\n" if/^\s*$/'
BAD_USER

 

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LEARN ABOUT MOJAVE

echo

ECHO(1) 						    BSD General Commands Manual 						   ECHO(1)

NAME

     echo -- write arguments to the standard output

SYNOPSIS

     echo [-n] [string ...]

DESCRIPTION

     The echo utility writes any specified operands, separated by single blank (' ') characters and followed by a newline ('
') character, to the
     standard output.

     The following option is available:

     -n    Do not print the trailing newline character.  This may also be achieved by appending 'c' to the end of the string, as is done by iBCS2
	   compatible systems.	Note that this option as well as the effect of 'c' are implementation-defined in IEEE Std 1003.1-2001
	   (``POSIX.1'') as amended by Cor. 1-2002.  Applications aiming for maximum portability are strongly encouraged to use printf(1) to sup-
	   press the newline character.

     Some shells may provide a builtin echo command which is similar or identical to this utility.  Most notably, the builtin echo in sh(1) does
     not accept the -n option.	Consult the builtin(1) manual page.

EXIT STATUS

     The echo utility exits 0 on success, and >0 if an error occurs.

SEE ALSO

     builtin(1), csh(1), printf(1), sh(1)

STANDARDS

     The echo utility conforms to IEEE Std 1003.1-2001 (``POSIX.1'') as amended by Cor. 1-2002.

BSD
								  April 12, 2003							       BSD
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