Shell Programming and Scripting

Dear all:

I want to write a script capable of reading specific rows and collumns of a table, into a variable.

Just imagine i have a file named table.dat which contains:

GENERAL INFORMATION
Col 1 Col2 Col3
1 1
2 2
3 3
4 4


What i want to do is reading, for each line, the data contents of col1 and col 2 (assigning them to variables, instead of writing them to files), in order to do some processing with those results.

Does anyone have a clue on how to accomplish this task?
Many thanks in advance

Luis Carvalheiro

One basic shell construct for doing this is:

Code:

while read COL_1 COL_2 COL_3
do
    <some code using your read variables COL_1, COL_2, COL_3>
done < table.dat

You can do something like this:

Code:

while read col1 col2
do
    echo "Col1 : $col1"
    echo "Col2 : $col2"
done < table.dat

Jean-Pierre.

I whish to thank the speed of your comments. I followed those instructions but I think i missed something. To make my intempts clear, i'll copy a general "table" whose contents i wish to read (a kind of cut&paste, basically)


---> table start
This is the table title, which doesn't need to be read (9)


COLUMN LINE COUNT :

1632 531 52.000
1641 617 52.000
1651 604 52.000
1651 605 52.000
1652 601 52.000
1652 604 52.000
1652 605 51.000
1652 606 52.000
----> table end

Ok. what i want is to read sequentially the numbers in COLUMN and LINE, i.e., 1632, 531; 1641, 617, and so on. For the time being, i don't care about the COUNT value.

I'm sorry if this sounds like a lame question...
Thankfull:

Luis

and what exactly in the posted solutions did not work?

Your text needs to have some known attributes such as a colon after your column headings for this to work:

Code:

{
IGNORE_FL=T
while read COLUMN LINE COUNT
do
    # Ignore blank lines
    if [[ ${#COUNT} -eq 0 || ${COLUMN} = --* ]]; then
        continue
    fi

    # COUNT variable will have the colon description terminator (":"), set IGNORE_FL to F and skip line
    if [[ ${COUNT} = *: ]]; then
        IGNORE_FL=F
        continue
    fi

    # Ignore all lines until actual columns are found
    if [[ ${IGNORE_FL} = T  ]]; then
        continue
    fi

    print "Column = ${COLUMN} / LINE = ${LINE}" 
done < file.dat 2> /dev/null
}

Also, be more specific when you indicate that something doesn't work. Provide examples and what you have tried in order to correct the issue. We're not really here to do your work but just to guide you along the way.

Once again, i thank you all for your patience in helping me. At the time being, the code looks like this

#!/bin/bash

#later, i'll copy teste.gif to teste$TIMESTAMP.gif
TIMESTAMP=`date "+%d%m%Y%H%M"`

#I don't want to change the original file, so let's make a copy
cp map.gif mapa.gif


while read COLUNA LINHA
do
echo "COLUNA : $col"
echo "LINHA : $lin"
convert -fill red -draw 'text $col,$lin "*"' mapa.gif teste.gif
done < below

As you can see, the basic idea is to plot a kind of a map, with the help of imagemagik's convert. The basic idea is to populate a pre-existing map with *'s, read from the file "below" (Columns 1 and 2).

The output from the code is erroneous, since i get the following error message (for each line...):

COLUNA :
LINHA :
convert: Non-conforming drawing primitive definition `text'.


Could you have the kindness of commenting the code?
Thanks again:
Luis