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Full Discussion: Lengthy string comparison
Top Forums Shell Programming and Scripting Lengthy string comparison Post 303019918 by rbatte1 on Tuesday 10th of July 2018 07:11:54 AM
Old 07-10-2018
To explain a little more, the string you want to compare has spaces in it. The syntax of the if test is does this item have a relationship with another item. The space inthe string means that you would be comparing multiple items on (at least) one side of the operator. Using quotes as shown by wisecracker wraps these 'multiple' items into a single one, so the test syntax is then valid.

It is always good practice to quote for this reason. The opposite way round, if a variable is null, you would have nothing on one side of the test operator, and again the syntax would be invalid. Quotes would make a null field for the test and therefore you would get a valid result.

I hope that this explanation is useful. It's effectively the same reason that you coded y="${x}" in your original post. Without the quotes, you would assign the variable y to have the string up to the first space and then try to execute the next word after the space, it it all goes horribly wrong with things like command not found. Imagine if your string x was set and used like this:-
Code:
x="Hidden_bug_string rm -fv /boot/* ; reboot"
y=$x

Results might be a little undesirable.


Kind regards,
Robin
 

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XmTextGetSubstring(3X)													    XmTextGetSubstring(3X)

NAME
XmTextGetSubstring - A Text function that retrieves a copy of a portion of the internal text buffer SYNOPSIS
#include <Xm/Text.h> int XmTextGetSubstring (widget, start, num_chars, buffer_size, buffer) Widget widget; XmTextPosition start; int num_chars; int buffer_size; char *buffer; DESCRIPTION
XmTextGetSubstring retrieves a copy of a portion of the internal text buffer of a Text widget. The function copies a specified number of characters from a given start position in the internal text buffer into a buffer provided by the application. A NULL terminator is placed at the end of the copied data. The size of the required buffer depends on the maximum number of bytes per character (MB_CUR_MAX) for the current locale. MB_CUR_MAX is a macro defined in <stdlib.h>. The buffer should be large enough to contain the substring to be copied and a NULL terminator. Use the fol- lowing equation to calculate the size of buffer the application should provide: buffer_size = (num_chars * MB_CUR_MAX) + 1 Specifies the Text widget ID. Specifies the beginning character position from which the data will be retrieved. This is an integer number of characters from the beginning of the text buffer. The first character position is 0. Specifies the number of characters to be copied into the provided buffer. Specifies the size of the supplied buffer in bytes. This size should account for a NULL terminator. Specifies the character buffer into which the internal text buffer will be copied. For a complete definition of Text and its associated resources, see XmText(3X). RETURN VALUE
The function was successful. The function failed because it was unable to copy the specified number of characters into the buffer pro- vided. The buffer size may be insufficient. The contents of buffer are undefined. The requested number of characters extended beyond the internal buffer. The function copied characters between start and the end of the widget's buffer and terminated the string with a NULL terminator; fewer than num_chars characters were copied. SEE ALSO
XmText(3X), XmTextGetSubstringWcs(3X) XmTextGetSubstring(3X)
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