09-27-2007
Quote:
Originally Posted by
Juha
Hi,
How can I replace x first characters from a string?
I have a file with... say 10000 entries as follows:
00123456781
00123456782
00123456783
...
What I want to do is change the leading "00" with for example "12"
The leading 00 can be in some files some other 1 or more digits e.g. "1" or "123" or what ever.
What would be the most efficient way of doing this as there might be even 20.000.000 entries in one file.
I wonder if the method could be embedded to a oneliner such as:
perl -i -p -e "s/old/new/g" filename
Thanks!
hey,
You can user sed.
sed 's/^[00]*/your replace string or number/' filename
I think you can use this when no. starts with 00* and in the starting of the line.
Otherwise you can use tr command to squeeze the multiple 0s.
visit: man tr
Thanks !!
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LEARN ABOUT FREEBSD
fnmatch
FNMATCH(3) BSD Library Functions Manual FNMATCH(3)
NAME
fnmatch -- test whether a filename or pathname matches a shell-style pattern
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <fnmatch.h>
int
fnmatch(const char *pattern, const char *string, int flags);
DESCRIPTION
The fnmatch() function matches patterns according to the rules used by the shell. It checks the string specified by the string argument to
see if it matches the pattern specified by the pattern argument.
The flags argument modifies the interpretation of pattern and string. The value of flags is the bitwise inclusive OR of any of the following
constants, which are defined in the include file <fnmatch.h>.
FNM_NOESCAPE Normally, every occurrence of a backslash ('') followed by a character in pattern is replaced by that character. This is done
to negate any special meaning for the character. If the FNM_NOESCAPE flag is set, a backslash character is treated as an ordi-
nary character.
FNM_PATHNAME Slash characters in string must be explicitly matched by slashes in pattern. If this flag is not set, then slashes are treated
as regular characters.
FNM_PERIOD Leading periods in string must be explicitly matched by periods in pattern. If this flag is not set, then leading periods are
treated as regular characters. The definition of ``leading'' is related to the specification of FNM_PATHNAME. A period is
always ``leading'' if it is the first character in string. Additionally, if FNM_PATHNAME is set, a period is leading if it
immediately follows a slash.
FNM_LEADING_DIR
Ignore ``/*'' rest after successful pattern matching.
FNM_CASEFOLD Ignore case distinctions in both the pattern and the string.
RETURN VALUES
The fnmatch() function returns zero if string matches the pattern specified by pattern, otherwise, it returns the value FNM_NOMATCH.
SEE ALSO
sh(1), glob(3), regex(3)
STANDARDS
The current implementation of the fnmatch() function does not conform to IEEE Std 1003.2 (``POSIX.2''). Collating symbol expressions, equiv-
alence class expressions and character class expressions are not supported.
HISTORY
The fnmatch() function first appeared in 4.4BSD.
BUGS
The pattern '*' matches the empty string, even if FNM_PATHNAME is specified.
BSD
July 18, 2004 BSD