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Top Forums Shell Programming and Scripting Help me to understand some regular expresions usage Post 302173514 by cfajohnson on Thursday 6th of March 2008 11:52:10 PM
Old 03-07-2008
Quote:
Originally Posted by alex_5161
Can someone explain me how those
restatements are constructed
Code:
        suffix=${name#*.}
        prefix=${main%%+([0-9])}
        num=10#${num}

1. What is the logic to use a reg-expr in variable name
2. In first string - the '#' seems to mean 'everithing after next
mached', but the '.' in reg-exp is a one character, here it seems it
used litteraly. Why?

You don't use regular expressions in parameter expansion; you use
filename expansion (a.k.a. wildcard) patterns.

See:
POSIX shell parameter expansions
 

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regcmp(1)							   User Commands							 regcmp(1)

NAME
regcmp - regular expression compile SYNOPSIS
regcmp [-] filename... DESCRIPTION
The regcmp command performs a function similar to regcmp and, in most cases, precludes the need for calling regcmp from C programs. Bypass- ing regcmp saves on both execution time and program size. The command regcmp compiles the regular expressions in filename and places the output in filename.i. OPTIONS
- If the - option is used, the output is placed in filename.c. The format of entries in filename is a name (C variable) followed by one or more blanks followed by one or more regular expressions enclosed in double quotes. The output of regcmp is C source code. Compiled regular expressions are represented as extern char vectors. filename.i files may thus be #included in C programs, or filename.c files may be compiled and later loaded. In the C program that uses the regcmp output, regex(abc,line) applies the regu- lar expression named abc to line. Diagnostics are self-explanatory. EXAMPLES
Example 1 Examples of the regcmp command. name "([A-Za-z][A-Za-z0-9_]*)$0" telno "({0,1}([2-9][01][1-9])$0){0,1} *" "([2-9][0-9]{2})$1[ -]{0,1}" "([0-9]{4})$2" The three arguments to telno shown above must all be entered on one line. In the C program that uses the regcmp output, regex(telno, line, area, exch, rest) applies the regular expression named telno to line. ENVIRONMENT VARIABLES
A general description of the usage of the LC_* environmental variables can be found in environ(5). LC_CTYPE Determines how regcmp handles characters. When LC_CTYPE is set to a valid value, regcmp can display and handle text and filenames containing valid characters for that locale. LC_MESSAGES Determines how diagnostic and informative messages are presented. This includes the language and style of the messages, and the correct form of affirmative and negative responses. In the "C" locale, the messages are presented in the default form found in the program itself (in most cases, U.S. English). ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Availability |SUNWtoo | |CSI |Enabled | +-----------------------------+-----------------------------+ SEE ALSO
regcmp(3C), attributes(5), environ(5) SunOS 5.11 Dec 20 1996 regcmp(1)
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