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Top Forums Shell Programming and Scripting Regular expression to match multiple lines? Post 302884196 by LessNux on Saturday 18th of January 2014 09:24:22 AM
Old 01-18-2014
Question Regular expression to match multiple lines?

Using a regular expression, I would like multiple lines to be matched.

By default, a period (.) matches any character except newline. However, (?s) and /s modifiers are supposed to force . to accept a newline and to match any character including a newline.

However, the following two perl statements that use (?s) and /s failed to find a pattern spanning multiple lines.

Code:
perl -p -e 's/a(?s).*f/z/' srcfile > dstfile

and
Code:
perl -p -e 's/a.*f/z/s' srcfile > dstfile

where the content of srcfile is
Code:
abc
def
ghi
jkl

which can be created by

Code:
cat > srcfile << EOF
abc
def
ghi
jkl
EOF


I wanted the regular expression to match the string consisting of two lines that starts with "a" and ends with "f".

In other words, I wanted to replace
Code:
abc
def
with z.

So, I wanted dstfile to become
Code:
z
ghi
jkl

However, the above perl statements failed. The regular expressions in the above perl statements matched nothing, making dstfile identical to srcfile.

What went wrong?

What regular expression would match multiple lines?

How can a perl or bash command line find a pattern spanning multiple lines in srcfile, replace it with another, and save the modified text into dstfile?

Many thanks, in advance.

Last edited by Scott; 01-18-2014 at 10:35 AM.. Reason: More code tags
 

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fnmatch(3C)															       fnmatch(3C)

NAME
fnmatch() - match filename patterns SYNOPSIS
DESCRIPTION
performs pattern matching as described in regexp(5) under By default, the rule qualifications for filename expansion do not apply; i.e., periods (dots) and slashes are matched as ordinary characters. This default behavior can be modified by using the flags described below. The flag argument modifies the interpretation of pattern and string. If which is defined in is set in flag, a slash character in string must be explicitly matched by a slash in pattern; it cannot be matched by either the asterisk or question mark special characters or by a bracket expression. If is set in flag, a leading period must be explicitly matched. It will not be matched by a bracket expression, question mark or asterisk. By default, a period is leading if it is the first character in string. If is set in flag, a period is leading if it is the first charac- ter in string or immediately follows a slash. If is not set in flag, a backslash character in pattern followed by any other character matches that second character in string. In par- ticular, matches a backslash in string. If is set, a backslash character is treated as an ordinary character. If flag is zero, the slash character and the period are treated as regular characters. If flag has any other value, the result is unde- fined. RETURN VALUE
If string matches the pattern specified by pattern, returns zero. Otherwise, returns non-zero. EXAMPLE
The following excerpt uses to check each file in a directory against the pattern pattern = "*.c"; while(dp = readdir(dirp)){ if((fnmatch(pattern, dp->d_name,0)) == 0){ /* do processing for match */ ... } } AUTHOR
was developed by OSF and HP. SEE ALSO
sh(1), glob(3C), thread_safety(5). STANDARDS CONFORMANCE
fnmatch(3C)
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