Perl validating numbers
(POSIX allows either behavior.) For example See shell script - OR in `expr match` - Unix & Linux Stack Exchange for some additional info. In cases when you use if often and need exact position of the substring in the source string you probably will be better off switching to Perl or any other scripting language that you know well. The option -b prints the byte offset of the string shown in the first position that you can extract from the result, but this is a perversion.You need numeric position you need to switch to Perl or AWK. In this case, it is recognizing that the 'o' in the characters ' Mozilla' matches the 4th character in ".."This using this as a test to see what happens.construct as you will be dealing with scripts infested with those old constructs pretty often.
Here are the most common "legacy integer comparison operators": String comparisons is all what left useful in this construct as for integer comparisons ((..)) construct is better and for file comparisons older [...] construct is equal.
This topic is discussed at greater length at String Operations in Shell Notes: It is considered better programming style to enclose all of the code in the if-then-else, but such code can get confusing if you are writing a long script in which you need to check for errors and bail out at several points along the way.]]
Sun OS and other `expr''s treat these as regular characters.
Recently it was also extended to case conversion using ^^ and ,, digrams This "ksh-originated" group of operators is the most popular and probably the most widely used group of string-handling operators so it makes sense to learn them, if only in order to be able to modify old scripts.
that can be used instead in many cases and they are definitely preferable in new scripts that you might write.
String operators allow you to manipulate the contents of a variable without resorting to AWK or Perl.
Modern shells such as bash 3.x or ksh93 supports most of the standard string manipulation functions, but in a very pervert, idiosyncratic way.