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Top Forums Shell Programming and Scripting How to replace all but the first 3 characters with sed? Post 302935025 by sea on Thursday 12th of February 2015 11:41:27 AM
Old 02-12-2015
Irritating,when i run my code using time i get:
Code:
+ ~/tmp $ cat ./leolson 
while read line
do
	len=${#line} ; [ $len -gt 3 ] && len=$(( $len - 3))
	tmp="$(printf '%*s' $len|sed s,\ ,*,g)"
	echo "${line:0:3}${tmp}"
done<file1

+ ~/tmp $ time bash ./leolson
aba*****
cdc*******
efe******
a*b****

real	0m0.007s
user	0m0.003s
sys	0m0.006s

I did a few runs, and felt tendency is more around 6-11 than 12+.
(had more 0.006 + 0.007 than everything else together)

Though, with MadeInGermany's 0.010 sec awk code i get 0.001 Smilie
Code:
time awk '{x=substr($0,N+1); gsub(".","*",x); print substr($0,1,N) x}' N=3 file1 > /dev/null

real	0m0.001s
user	0m0.000s
sys	0m0.001s

And your perl code behaves quite irrrational:
Code:
+ ~/tmp $ time perl -pe 's/(?<=...)./*/g' file1 >/dev/null

real	0m0.119s
user	0m0.003s
sys	0m0.002s
+ ~/tmp $ time perl -pe 's/(?<=...)./*/g' file1 >/dev/null

real	0m0.006s
user	0m0.002s
sys	0m0.004s

I find the time diffrence quite immmense and confusing.
Sure, some mili-secs diffrence can happen - but by factor 19.8:1?

Last edited by sea; 02-12-2015 at 01:01 PM..
 

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SSP(3)							   BSD Library Functions Manual 						    SSP(3)

NAME
ssp -- bounds checked libc functions LIBRARY
Buffer Overflow Protection Library (libssp, -lssp) SYNOPSIS
#include <ssp/stdio.h> int sprintf(char *str, const char *fmt, ...); int vsprintf(char *str, const char *fmt, va_list ap); int snprintf(char *str, size_t len, const char *fmt, ...); int vsnprintf(char *str, size_t len, const char *fmt, va_list ap); char * gets(char *str); char * fgets(char *str, int len, FILE *fp); #include <ssp/string.h> void * memcpy(void *str, const void *ptr, size_t len); void * memmove(void *str, const void *ptr, size_t len); void * memset(void *str, int val, size_t len); char * strcpy(char *str, const char *ptr, size_t len); char * strcat(char *str, const char *ptr, size_t len); char * strncpy(char *str, const char *ptr, size_t len); char * strncat(char *str, const char *ptr, size_t len); #include <ssp/strings.h> void * bcopy(const void *ptr, void *str, size_t len); void * bzero(void *str, size_t len); #include <ssp/unistd.h> ssize_t read(int fd, void *str, size_t len); int readlink(const char * restrict path, char * restrict str, size_t len); int getcwd(char *str, size_t len); DESCRIPTION
When _FORTIFY_SOURCE bounds checking is enabled as described below, the above functions get overwritten to use the __builtin_object_size(3) function to compute the size of str, if known at compile time, and perform bounds check on it in order to avoid data buffer or stack buffer overflows. If an overflow is detected, the routines will call abort(3). To enable these function overrides the following should be added to the gcc(1) command line: ``-I/usr/include/ssp'' to override the standard include files and ``-D_FORTIFY_SOURCE=1'' or ``-D_FORTIFY_SOURCE=2''. If _FORTIFY_SOURCE is set to 1 the code will compute the maximum possible buffer size for str, and if set to 2 it will compute the minimum buffer size. SEE ALSO
gcc(1), __builtin_object_size(3), stdio(3), string(3), security(7) HISTORY
The ssp library appeared NetBSD 4.0. BSD
March 21, 2011 BSD
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