[SOLVED] An elagant solution for: C to Shell? About strings

Question

Hello:
I'm a newbie at Shell. I would like to traduce a C code to Shell. I would ike to make it compact BUT legible (not so cryptic as Shell could allow).
This is the original C code (the explanation of the files -input- are bellow, in the shell part):
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#define BUFF_SIZE 512
static void Check(char *InputFile, char *OutputFile)
FILE *fpi,*fpo;
char Buffer[BUFF_SIZE+1];
int CntRec = 0;
fpi = fopen(InputFile,"r");
fpo = fopen(OutputFile,"w");
if (fpi) {
memset(Buffer,0,sizeof(Buffer));
while (fgets(Buffer,BUFF_SIZE,fpi)) {
if ((strlen(Buffer) > 100) && (!memcmp(Buffer,"5698",4))) {
fputs(Buffer,fpo);
CntRec++;
memset(Buffer,0,sizeof(Buffer));
fclose(fpi);
fclose(fpo);
printf("Number of registers = [%d]\n",CntRec);
This is my first attempt with Shell:
#!/bin/bash
# Program:
# Gomy, FILL THIS, DO NOT FORGET!
# Synopsis:
# Read from a file each line, which has the following format:
# nnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnl000000000000nnnnnnnSTRING [... more n and l's]
# where:
# n is a <positive int>
# l is a <char> (no special chars)
# The program should check that each line of the file:
# I) Has at least a [MIN_LENGHT] character length.
# II) The first characters of the string has a pre-defined
# pattern, in this case: MATCH_PATTERN
# If the line do not match [i] and [II], it should be copied
# in an output file for further analysis. Also, the number
# of those cases must be shown.
MIN_LENGTH=100
MATCH_PATTERN="5698"
counter = 0
#Read all the lines of the file.
while read line
do
len=${#line} #Store the length
pattern=${line:0:4} #Store the first x chars for contrast with [MATCH_PATTERN]
if [[ "$len" -lt "$MIN_LENGTH" && "$pattern" = $MATCH_PATTERN ]]; then
$line > output.txt
$counter++
fi
done
exit
Well, the If works. Never the less:
I) why I have to use a [[...]] instead of [].
II) The $line > output.txt is not working for me. It says: [STRING FROM FILE] command nor found.
III) Also the counter, with the ++  is not working.
IV) When I run the program, I do it like:
sh check.sh < test.txt
(or ./check <test.txt)
But I would like to do it like:
sh check.sh input.txt output.txt
I also tried to do it with awk, but my attempt failed:
awk '{ line=$0; print (length($line)) }' input.txt
could not manage the if's and others conditions so well!
Well, if you could give some tips, I would be delighted.
Thank you!
Last edited by gromlok (2011-09-25 16:39:39)

Answer 1

Hello: Thank for your answer, I took some of your code, and did this:
# Check the number of arguments that could be passed.
if [[ ${#@} != 2 ]]; then
echo "Wrong # of parameters...Use: check<inputfile> <outputfile>\n"
exit
fi
#Inputfile: is in position 1 on the ARGS
inputfile=$1
#Outputfile: is in position 2 on the ARGS
outputfile=$2
MIN_LENGTH=100
MATCH_PATTERN="5698"
#Read all the lines of the file.
# Notice: "read -r" Do not treat a backslash character in any special way.
# Consider each backslash to be part of the input line.
while read -r line
do
len=${#line} #Store the length
pattern=${line:0:4} #Store the first x chars for contrast with [MATCH_PATTERN]
if [[ "$len" -lt "$MIN_LENGTH" && "$pattern" = $MATCH_PATTERN ]]; then
(( ++count ))
echo "$line" >> "$outputfile"
fi
done < "$inputfile"
printf 'Number of registers: %s\n' "$count"
But I have some questions:
I) In your code, why use:
done < inputfile
. I don't get it. With the "while" is not enough to read all the file.
II) Is it OK to use inputfile=$1 and outputfile=$2 that way?
III) I did not find why  (( ++count )) works in shell! Using
let count = count + 1
works, but that way you did it is more elegant.
IV) Puting "exit" at the end is redundant?
Thanks for the guide, is more compact that the one I was/am reading
Last edited by gromlok (2011-09-25 04:03:44)