Trying to add text at the end of multiple lines in a txt file

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I have a project in Bash and I need a way of calculating averages of students and adding those averages in a text file. The text file is the following:

:NOM Prenom:CODE                :.Tp1 :.Intra:.Tp2 :.Tp3 :.Final :.TP4 :.Moy:.Lettre:
actarusx:Actarus  :ACTA28658105 : 45.5: 75.00:100.0: 95.0:  48.50: 90.0:  
alcorxxx:Alcor    :ALCO18083408 : 83.0: 64.75: 95.0: 87.5:  74.00: 97.0:  
venusiax:Venusia  :VENU13097708 : 83.0: 55.00: 95.0: 87.5:  41.50: 97.0:  
phenicia:Phenicia :PHEN14100790 : 94.0: 50.50: 95.0: 95.0:  59.50: 99.0:  
mizarxxx:Mizar    :MIZA22128106 : 98.0: 95.50: 95.0:100.0:  80.50: 90.0:  
procyonx:Procyon  :PROC01033701 : 99.0: 99.50:100.0: 95.0:  98.00:100.0:  
flamxxxx:Flam     :FLAM26077904 : 89.0: 37.25: 97.5: 87.5:  63.50: 97.0:  
johannxx:johann   :JOHA23058000 : 94.0: 99.25:100.0: 95.0:  36.00:100.0:  
wrightxx:Wright   :WRIG21058103 : 99.0: 100.0:100.0:100.0:  100.0: 97.0:  
cragxxxx:Grag     :CRAG05018002 : 99.0: 90.00: 90.0:100.0:  97.00: 99.0:  
malaxxxx:Mala     :MALA09557914 : 96.0: 69.50:100.0:100.0:  34.00: 47.0:

I want to calculate the total average of TP1,2,3,4, Intra and Final. Once I have the average for each student (one student per line), I want to add the average under the column called Moy:. Note: For some reason, the categories all got moved around so the first line of floats is associated with tp1 and so forth.

At the moment I have:

nbline=0
while read line; do
   if[ $nbline -eq 0 ]; then #To skip the first line with each categories
      let nbline+=1
   else
     # Code that allows me to get the grades for each categories (already provided by the teacher)
     # eg. for the first student the code will do tp1=45.5, intra=75, etc...
     # Code that allows me to calculate the average (already provided by the teacher)
     # moy is the average found

Once I find moy, I'm not sure how to add it in the column Moy: of each student. This is my first time coding in unix/linux and my teacher didn't spend a lot of time (if any at all) teaching us the different commands so help would be greatly appreciated.

Thank you very much

bash
3 Answers

Simple is Good

λ cat input.txt
:NOM Prenom:CODE                :.Tp1 :.Intra:.Tp2 :.Tp3 :.Final :.TP4 :.Moy:.Lettre:
actarusx:Actarus  :ACTA28658105 : 45.5: 75.00:100.0: 95.0:  48.50: 90.0:
alcorxxx:Alcor    :ALCO18083408 : 83.0: 64.75: 95.0: 87.5:  74.00: 97.0:
venusiax:Venusia  :VENU13097708 : 83.0: 55.00: 95.0: 87.5:  41.50: 97.0:
phenicia:Phenicia :PHEN14100790 : 94.0: 50.50: 95.0: 95.0:  59.50: 99.0:
mizarxxx:Mizar    :MIZA22128106 : 98.0: 95.50: 95.0:100.0:  80.50: 90.0:
procyonx:Procyon  :PROC01033701 : 99.0: 99.50:100.0: 95.0:  98.00:100.0:
flamxxxx:Flam     :FLAM26077904 : 89.0: 37.25: 97.5: 87.5:  63.50: 97.0:
johannxx:johann   :JOHA23058000 : 94.0: 99.25:100.0: 95.0:  36.00:100.0:
wrightxx:Wright   :WRIG21058103 : 99.0: 100.0:100.0:100.0:  100.0: 97.0:
cragxxxx:Grag     :CRAG05018002 : 99.0: 90.00: 90.0:100.0:  97.00: 99.0:
malaxxxx:Mala     :MALA09557914 : 96.0: 69.50:100.0:100.0:  34.00: 47.0:

awk -F: 'NR==1;NR>1{print $0 ($4+$5+$6+$7+$8+$9)/6}' input.txt

:NOM Prenom:CODE                :.Tp1 :.Intra:.Tp2 :.Tp3 :.Final :.TP4 :.Moy:.Lettre:
actarusx:Actarus  :ACTA28658105 : 45.5: 75.00:100.0: 95.0:  48.50: 90.0:  75.6667
alcorxxx:Alcor    :ALCO18083408 : 83.0: 64.75: 95.0: 87.5:  74.00: 97.0:  83.5417
venusiax:Venusia  :VENU13097708 : 83.0: 55.00: 95.0: 87.5:  41.50: 97.0:  76.5
phenicia:Phenicia :PHEN14100790 : 94.0: 50.50: 95.0: 95.0:  59.50: 99.0:  82.1667
mizarxxx:Mizar    :MIZA22128106 : 98.0: 95.50: 95.0:100.0:  80.50: 90.0:  93.1667
procyonx:Procyon  :PROC01033701 : 99.0: 99.50:100.0: 95.0:  98.00:100.0:  98.5833
flamxxxx:Flam     :FLAM26077904 : 89.0: 37.25: 97.5: 87.5:  63.50: 97.0:  78.625
johannxx:johann   :JOHA23058000 : 94.0: 99.25:100.0: 95.0:  36.00:100.0:  87.375
wrightxx:Wright   :WRIG21058103 : 99.0: 100.0:100.0:100.0:  100.0: 97.0:  99.3333
cragxxxx:Grag     :CRAG05018002 : 99.0: 90.00: 90.0:100.0:  97.00: 99.0:  95.8333
malaxxxx:Mala     :MALA09557914 : 96.0: 69.50:100.0:100.0:  34.00: 47.0:  74.4167

Explanation

  1. -F: sets : as the field separator
  2. A missing { action } means print the line. For example, the following commands are identical:
    1. awk '1{ print $0 }
    2. awk '1{ print }
    3. awk '1'
  3. Here we use 1 as pattern condition. awk treats non-empty string and non-zero number as true. For example, the following commands are identical:
    1. awk '1'
    2. awk '"foo"'
  4. awk concatenations are indicated by white spaces thus print $0 ($4+$5+$6+$7+$8+$9)/6 would print the whole record $0 followed by ($4+$5+$6+$7+$8+$9)/6.
user_10094420

Would you please try the following:

#!/bin/bash

while read -r line; do
    if (( nr++ == 0 )); then                    # header line
        echo "$line"
    else
        mapfile -d: -t a <<< "$line"            # assign array "a" to the columns
        ave=$(echo "scale=2; ( $(IFS=+; echo "${a[*]:3:6}") ) / 6" | bc)
        printf "%s%6s\n" "$line" "$ave"
    fi
done < file.txt

Output:

:NOM Prenom:CODE                :.Tp1 :.Intra:.Tp2 :.Tp3 :.Final :.TP4:.Moy:.Lettre:
actarusx:Actarus  :ACTA28658105 : 45.5: 75.00:100.0: 95.0:  48.50: 90.0: 75.66
alcorxxx:Alcor    :ALCO18083408 : 83.0: 64.75: 95.0: 87.5:  74.00: 97.0: 83.54
venusiax:Venusia  :VENU13097708 : 83.0: 55.00: 95.0: 87.5:  41.50: 97.0: 76.50
phenicia:Phenicia :PHEN14100790 : 94.0: 50.50: 95.0: 95.0:  59.50: 99.0: 82.16
mizarxxx:Mizar    :MIZA22128106 : 98.0: 95.50: 95.0:100.0:  80.50: 90.0: 93.16
procyonx:Procyon  :PROC01033701 : 99.0: 99.50:100.0: 95.0:  98.00:100.0: 98.58
flamxxxx:Flam     :FLAM26077904 : 89.0: 37.25: 97.5: 87.5:  63.50: 97.0: 78.62
johannxx:johann   :JOHA23058000 : 94.0: 99.25:100.0: 95.0:  36.00:100.0: 87.37
wrightxx:Wright   :WRIG21058103 : 99.0: 100.0:100.0:100.0:  100.0: 97.0: 99.33
cragxxxx:Grag     :CRAG05018002 : 99.0: 90.00: 90.0:100.0:  97.00: 99.0: 95.83
malaxxxx:Mala     :MALA09557914 : 96.0: 69.50:100.0:100.0:  34.00: 47.0: 74.41
  • mapfile -d: -t a <<< "$line" splits the input line on colons and assign array a to the columns.
  • $(IFS=+; echo "${a[*]:3:6}") outputs the columns from the 4th to the 9th delimited by + sign so the bc command can caluculate the sum of the columns.
  • If you want to tweak the number of decimal digits of the average, modify the value to -scale=2 and the width %6s in printf format.
user_85723800 
LC_ALL="C"

start_col=4
end_col=9
output_col=10
delimiter=":"

awk \
        -F"$delimiter" \
        -v "start=$start_col" \
        -v "end=$end_col" \
        -v "output=$output_col" '
        BEGIN {OFS = FS}
        NR == 1 { print }
        NR !=1 {
          sum=0
          for (i=start; i<=end; i++) sum=sum+$i
          $(output)=" "sprintf("%.2f", sum/((end+1)-start))
          print
}' file.txt

Output:

:NOM Prenom:CODE                :.Tp1 :.Intra:.Tp2 :.Tp3 :.Final :.TP4 :.Moy:.Lettre:
actarusx:Actarus  :ACTA28658105 : 45.5: 75.00:100.0: 95.0:  48.50: 90.0: 75.67
alcorxxx:Alcor    :ALCO18083408 : 83.0: 64.75: 95.0: 87.5:  74.00: 97.0: 83.54
venusiax:Venusia  :VENU13097708 : 83.0: 55.00: 95.0: 87.5:  41.50: 97.0: 76.50
phenicia:Phenicia :PHEN14100790 : 94.0: 50.50: 95.0: 95.0:  59.50: 99.0: 82.17
mizarxxx:Mizar    :MIZA22128106 : 98.0: 95.50: 95.0:100.0:  80.50: 90.0: 93.17
procyonx:Procyon  :PROC01033701 : 99.0: 99.50:100.0: 95.0:  98.00:100.0: 98.58
flamxxxx:Flam     :FLAM26077904 : 89.0: 37.25: 97.5: 87.5:  63.50: 97.0: 78.62
johannxx:johann   :JOHA23058000 : 94.0: 99.25:100.0: 95.0:  36.00:100.0: 87.38
wrightxx:Wright   :WRIG21058103 : 99.0: 100.0:100.0:100.0:  100.0: 97.0: 99.33
cragxxxx:Grag     :CRAG05018002 : 99.0: 90.00: 90.0:100.0:  97.00: 99.0: 95.83
malaxxxx:Mala     :MALA09557914 : 96.0: 69.50:100.0:100.0:  34.00: 47.0: 74.42
user_41778280
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