mjhjmtu

So I have a subject folder which contains subjects such as :

• Geography


• Math

These subjects are files.
And each one of them contain the name of a student with his mark.

Sor for example it will be,

For Geography

• Mattew 15


• Elena 14

And Math :

• Matthew 10


• Elena 19

I also have a student folder which is empty for now.
And the purpose of this folder is to put inside of it :

1. The name of the student as the name of the file;


2. The marks of all subjets this student received.

So here is my code :

#### Subjects folder #####
GEOGRAPHY="/home/subject/geography"
MATH="/home/subject/math"

##### Registration student #####
studentMatthew="/home/student/Matthew"
Geo_Matthew=$(grep "Matthew" "$GEOGRAPHY" | cut -d' ' -f2) > "$studentMatthew"
Math_Matthew=$(grep "Matthew" "$MATH" | cut -d' ' -f2) > "$studentMatthew"

studentElena="/home/student/Elena"
Geo_Elena=$(grep "Elena" "$GEOGRAPHY" | cut -d' ' -f2) > "$studentElena"
Math_Elena=$(grep "Elena" "$MATH" | cut -d' ' -f2) > "$studentElena"


##### SHOW RESULT #####
echo "Geography" >> "$studentMatthew" "$Geo_Matthew"
echo "Math" >> "$studentMatthew" "$Geo_Matthew"

echo "Geography" >> "$studentElena" "$Geo_Elena"
echo "Math" >> "$studentElena" "$Math_Elena"

This works perfectly.
But it is not a very good practice to write it this way.

Because if for example I add another student let's say Patrick, I'll have to manually add his marks for both Geography and Math.

So it'll be :

##### Registration Patrick #####
studentPatrick="/home/student/Patrick"
Geo_Patrick=$(grep "Patrick" "$GEOGRAPHY" | cut -d' ' -f2) > "$studentPatrick"
Math_Patrick=$(grep "Patrick" "$MATH" | cut -d' ' -f2) > "$studentPatrick"

##### SHOW RESULT PATRICK #####
echo "Geography" >> "$studentPatrick" "$Geo_Patrick"
echo "Math" >> "$studentPatrick" "$Math_Patrick"

And it'll be redundant..

So I was wondering,

Is there a way to refactor this code into a loop? So if I add a new student, I won't have to manually write it again ?

for subjfile in /home/subject/*; do
 awk -v subj="$(basename "$subjfile")" ' print subj, $2 >>"/home/student/" $1 ' "$subjfile"
done

This would iterate over all the subject files. The $subjfile value would be something like /home/subject/Math or /home/subject/Geography etc., depending on what subjects were available.

The awk program would open each of these files in turn and print the subject name (which is the "basename" of the pathname in $subjfile, i.e. Math or Geography) followed by the mark in that subject (column 2 of the $subjfile file).

This would be written to "/home/student/" $1 which is a pathname under /home/student. The $1 is the first column of the $subjfile file, which is the name of the student.

The code assumes that the student directory is empty when the script starts running (or it will append to the files in there).

Running on the given data (including the misspelling of one of the names), this would create three files in /home/student:

$ cat Elena
Geography 14
Math 19

$ cat Mattew
Geography 15

$ cat Matthew
Math 10

Note that the student names are picked from the files under /home/subject and never hard-coded in the script. Also, the various subjects depends on what files are available in the /home/subject directory.

Would you want to do this without involving awk:

for subjfile in /home/subject/*; do
 subject=$( basename "$subjfile" )
 while read -r name marks; do
 printf '%s %dn' "$subject" "$marks" >>"/home/student/$name"
 done <"$subjfile"
done

Off the top of my head, you do something like this:

# loop over all files in the student directory
for studentfile in /home/student/*; do
 # take just the name of the student (the file name without the path)
 studentname="$studentfile##*/"

 # uncomment the next line to clear the student files before populating them
 # > "$studentfile" 

 # loop over all subject files
 for subject in /home/subject/*; do
 # again, remove the path
 subject="$subject##*/"
 grep "$studentname" "$subject" | cut -d' ' -f2 >> "$studentfile"
 done
done

This assuming that the file names for the students and subjects are exactly the same as the labels used for them within the files and that there exists a file already for each student.

The $var##*/ expansion takes the value of $var with the longest prefix matching */ removed, i.e. it leaves just the path. We need both for the student, since we use just Matthew for the grep but /home/student/Matthew for the output redirection.

Note that your assignment Geo_Matthew=$(grep "Matthew" "$GEOGRAPHY" | cut -d' ' -f2) > "$studentMatthew" has an extra redirection in it, the assignment doesn't create any output, so the redirection only truncates the file named in $studentMatthew. You can just redirect the output of grep to the file and remove the command substitution, the Geo_Matthew variable, and the later echo.

This would be better done with an awk or Perl script instead of a shell script, but the above is a possible way to arrange the commands you have in loops.