UNIX for Dummies Questions & Answers

input file: 200006-07file.txt
145 35 10 3
147 35 12 4
146 36 11 3
145 34 12 5
143 31 15 4
146 30 14 5

desired output files:
200006-07_003.txt (this contains:)
145 35 10 3
146 36 11 3

200006-07_004.txt
147 35 12 4
143 31 15 4

200006-07_004.txt
145 34 12 5
146 30 14 5

200006-07_005.txt

sort -n -k4 200006-07file.txt > file.tmp

awk '$4==3 {print}' file.tmp > 200006-07_003.txt
awk '$4==4 {print}' file.tmp > 200006-07_004.txt
awk '$4==5 {print}' file.tmp > 200006-07_005.txt

awk '
FNR == 1 {
        # Get filename base and clear list of output files for this input file.
        if((i = index(FILENAME, "file.txt")) == 0) {
                printf("Filenames (\"%s\") does not end in \"file.txt\"\n",
                        FILENAME)
                exit 1
        }
        base = substr(FILENAME, 1, i - 1)
        for (i in outlist) delete outlist[i]
}
{       # Generate output filename for this line:
        of = sprintf("%s_%03d.txt", base, $4)
        if(lf != of) {
                # Close previous output file, if there was one.
                if(lf != "") close(lf)
                # If this is the 1st time for a new output file, add it to the
                # list of output files and remove any existing file with that
                # name.
                if(!($4 in outlist)) {
                        # Remove any existing file with this name:
                        system("rm -f " of)
                        # Save this index in outlist:
                        outlist[$4]
                }
                lf = of
        }
        # Save the current line in the current output file:
        print >> lf
}' 200006-07file.txt