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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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fmt(1)								   User Commands							    fmt(1)

NAME
fmt - simple text formatters SYNOPSIS
fmt [-cs] [-w width | -width] [inputfile]... DESCRIPTION
fmt is a simple text formatter that fills and joins lines to produce output lines of (up to) the number of characters specified in the -w width option. The default width is 72. fmt concatenates the inputfiles listed as arguments. If none are given, fmt formats text from the standard input. Blank lines are preserved in the output, as is the spacing between words. fmt does not fill nor split lines beginning with a `.' (dot), for compatibility with nroff(1). Nor does it fill or split a set of contiguous non-blank lines which is determined to be a mail header, the first line of which must begin with "From". Indentation is preserved in the output, and input lines with differing indentation are not joined (unless -c is used). fmt can also be used as an in-line text filter for vi(1). The vi command: !}fmt reformats the text between the cursor location and the end of the paragraph. OPTIONS
-c Crown margin mode. Preserve the indentation of the first two lines within a paragraph, and align the left margin of each subsequent line with that of the second line. This is useful for tagged paragraphs. -s Split lines only. Do not join short lines to form longer ones. This prevents sample lines of code, and other such for- matted text, from being unduly combined. -w width | -width Fill output lines to up to width columns. OPERANDS
inputfile Input file. ENVIRONMENT VARIABLES
See environ(5) for a description of the LC_CTYPE environment variable that affects the execution of fmt. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Availability |SUNWcsu | +-----------------------------+-----------------------------+ SEE ALSO
nroff(1), vi(1), attributes(5), environ(5) NOTES
The -width option is acceptable for BSD compatibility, but it may go away in future releases. SunOS 5.11 9 May 1997 fmt(1)
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