It is a mistake to use regular expression matching when the "patterns" to be matched are not patterns but literal strings. Consider what would happen if one of the literal strings contains a regular expression metacharacter. Perhaps that's extremely unlikely with usernames, but it should be considered.
Even if regular expression matching is disabled, there is still the problem of substring matches, since there is no anchoring in effect.
To disable both regular expression matching (in favor of fixed string matching) and (assuming one username per line) to require whole-line matching to prevent substring matches:
There is no point in sorting when using grep. Whatever is gained (when a pattern near the head of the pattern list matches one of the first lines of data) is surrendered (when later matches consistently nearly-exhaust the pattern list) and sorting overhead is never recovered.
If you are going to sort the files, comm would be a more efficient alternative.
can anyone point me to a comparison of *nix file systems ?
i think i prefer a journalling fs
but i would like to see a comparison between several fs's before i make up my mind (2 Replies)
I need some help which would probably be for most of you a simple script.
I need to read in the data from a .dat file and then compare avg to see who is the highest avg. Here is my script so far.
#!/bin/ksh
#reading in the data from lab3.dat
filename=$1
while read name o1 o2 o3 o4 o5 o6... (0 Replies)
hi
I have 2 files to comapre ,in file a sible column it is numbers,in file b2 numbers and other values with coma separated.
i want compare numbers in file a with file b,and the out put put should be in C with numbers in both file a and b along with other columns of file b.
i used folowing... (7 Replies)
what is the easy way to compare checksums of sereral paramters by script:
for example:
#im creating a file containing a list of checksum parameters
cksum /opt/LGTOaam51/data_source_types/UX_File_System/* > t1
#and another one
cksum /opt/LGTOaam51/data_source_types/UX_File_System2/* > t2
... (2 Replies)
I have an array @name with the below contents (index 7 and 8 are names):
1|1|2|2|I|2|0|DUNN|LACY||||||
2|2|2|2|I|2|0|KOFE|ROGER||||||
3|3|2|2|A|2|0|KOFOED|ROBERT||||||
3|4|2|2|A|2|0|KOFOED|ROBERT||||||
3|5|2|2|A|2|0|KOFOED|ROBERT||||||
2|7|2|2|I|2|0|WILLIAMSON|JAMES||||||... (4 Replies)
Is there a way to compare the permission string of two files and output the string if they match?
For ex:
-rw-r--r-- 1 user newuser 0 2009-03-12 16:45 file2
-rw-r--r-- 1 user newuser 0 2009-03-12 16:46 fileone
output:
-rw-r--r--
If they don't match output will be just... (3 Replies)
hi guys
i need a program that can compare a value read from a com-port and one from the terminal.
can somebody help me???
using linux kernel 2.6.14-M5
can only use standard function in sh and bash... (5 Replies)
Hi friends,
I would like to compare two dates in an IF statement.
This is what I am trying, but it doesn't work.
date=20120122
minus=6
if ; then
...
fi
what would the IF clause looks like?
Thanks! :) (5 Replies)
Discussion started by: kokoro
5 Replies
LEARN ABOUT REDHAT
ppmtopgm
ppmtopgm(1) General Commands Manual ppmtopgm(1)NAME
ppmtopgm - convert a portable pixmap into a portable graymap
SYNOPSIS
ppmtopgm [ppmfile]
DESCRIPTION
Reads a portable pixmap as input. Produces a portable graymap as output. The output is a "black and white" rendering of the original
image, as in a black and white photograph. The quantization formula used is .299 r + .587 g + .114 b.
Note that although there is a pgmtoppm program, it is not necessary for simple conversions from pgm to ppm , because any ppm program can
read pgm (and pbm ) files automatically. pgmtoppm is for colorizing a pgm file. Also, see ppmtorgb3 for a different way of converting
color to gray. And ppmdist generates a grayscale image from a color image, but in a way that makes it easy to differentiate the original
colors, not necessarily a way that looks like a black and white photograph.
QUOTE
Cold-hearted orb that rules the night
Removes the colors from our sight
Red is gray, and yellow white
But we decide which is right
And which is a quantization error.
SEE ALSO pgmtoppm(1),ppmtorgb3(1),rgb3toppm(1),ppmdist(1),ppm(5),pgm(5)AUTHOR
Copyright (C) 1989 by Jef Poskanzer.
10 April 2000 ppmtopgm(1)