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Full Discussion: test for a blank string
Top Forums Shell Programming and Scripting test for a blank string Post 302596794 by aoussenko on Wednesday 8th of February 2012 09:48:13 AM
Old 02-08-2012
test for a blank string

Hi guys
I am performing a simple test for a blank string with the following code:
Code:
   if [[ ! ${user_input} =~ [^[:space:]] ]] ; then
        echo "Blanks are NOT a valid input "
        return 1
   fi

The above fails giving a syntax error message:
Code:
syntax error at line 142 : `=~' unexpected

I am in ksh88

is there any other way to test for a blank string. (it should have blanks and/or tabs to be blank) ?
or maybe someone can tell me what am I doing wrong in the code above. Thanks a lot for advice -A
 

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FBB::mlm(3bobcat)                                             OFoldStream manipulator                                            FBB::mlm(3bobcat)

NAME
FBB::mlm - Manipulator modifying left margins of OFoldStream objects SYNOPSIS
#include <bobcat/ofoldstream> or #include <bobcat/ofoldstreambuf> Linking option: -lbobcat DESCRIPTION
The mlm class implements a manipulator that can be inserted into OFoldStream objects to modify the stream's left margin by a requested amount. The request cannot result in a negative left margin value. If a negative left margin would be the arithmetic result of the request then left margin 0 will silently be used. Depending on the tab-setting of the OFoldStream the inserted value represents the number of blank space characters or the number of tab-characters that will be added to the left margin. The request will be processed at the next newline character or std::flush or std::endl manipulator that is inserted into the stream. If a line is still empty once an mlm object and a flush manipulator are inserted into the stream then the new left margin will be effective at the next word inserted into that line (cf., the example section below) A bad_cast exception is thrown when the manipulator is inserted into an ostream that is not using a OFoldStreambuf buffer. NAMESPACE
FBB All constructors, members, operators and manipulators, mentioned in this man-page, are defined in the namespace FBB. INHERITS FROM
- CONSTRUCTOR
o mlm(int addValue): The standard copy constructor is available. MEMBER FUNCTIONS
There are no public or protected member functions in this class. EXAMPLE
#include <iostream> #include <bobcat/ofoldstream> using namespace std; using namespace FBB; int main() { OFoldStream out(cout, 0, 80); out << "hello world (left margin is 0)" << mlm(4) << " " "this uses a 4 character wide left margin " << mlm(-10) << flush << "left margin -6 changed to 0, active on this line "; return 0; } FILES
bobcat/mlm - defines the class interface SEE ALSO
bobcat(7), manipulators(3bobcat), lm(3bobcat), ofoldstream(3bobcat) BUGS
None Reported. DISTRIBUTION FILES
o bobcat_3.01.00-x.dsc: detached signature; o bobcat_3.01.00-x.tar.gz: source archive; o bobcat_3.01.00-x_i386.changes: change log; o libbobcat1_3.01.00-x_*.deb: debian package holding the libraries; o libbobcat1-dev_3.01.00-x_*.deb: debian package holding the libraries, headers and manual pages; o http://sourceforge.net/projects/bobcat: public archive location; BOBCAT
Bobcat is an acronym of `Brokken's Own Base Classes And Templates'. COPYRIGHT
This is free software, distributed under the terms of the GNU General Public License (GPL). AUTHOR
Frank B. Brokken (f.b.brokken@rug.nl). libbobcat1-dev_3.01.00-x.tar.gz 2005-2012 FBB::mlm(3bobcat)
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