Technion Bash Questions

The questions and solutions can be found here or on our moodle class website

Bash Special Variables – MyLinuxPlace

Bash Scripting Tutorial for Beginners - LinuxConfig.org

Winter 2014 Moed A - Exam 15-1-a

exam-grades.txt

123 65
789 89
234 95

hmwk-grades.txt

123 70
234 80
789 100

Lets sort them by ID

$ cat exam-grades.txt hmwk-grades.txt | sort -n
123 65
123 70
234 80
234 95
789 100
789 89

• -n Option : To sort a file numerically (here we want by ID).

• Alphabetical order is the default (no flags)

Answer

calc1:
#!/bin/bash
cat exam-grades hmwk-grade  | sort -n  | ./calc2

calc2
#!/bin/bash
while read line; do #read 1st line
   ls1=( $line ) #get line from exam-grades, put both values into array, ls-line split
        read line #read 2nd line
        ls2=( $line ) #get line from hmwk-grades
         (( sum=${ls1[1]}*3/4+${ls2[1]}*1/4+0 ))  # ls1[1] and ls2[1] are the grades
        echo ${ls1[0]} $sum
done

My Solution looks a bit different

while read id_t  g_t; do # read id into id_t, grade into g_t
    read id_h  g_h
    sum=$(( ${g_t}*3/4+${g_h}*1/4+0 ))
    echo ${id_t} $sum
done

Winter 2015 Moed A - Exam 16-1-a

$ sed -n '2,$p' comb | ./calc.sh
37000 9250

sed will read from line 2 until the end

#! /bin/bash
(( sum=0 ))
(( count=0 ))
while read line; do
    line_split=($line)
    (( count+=1 ))
    (( sum+=${line_split[3]}+0 ))
done

(( avg=$sum/$count ))
echo "$sum" "$avg"

Part Bet

Before let review the following:

jobs=($@)
echo "$len"
for job in ${jobs[@]}; do
    echo $job
done

$ ./avg.sh hello world shalom
3
hello
world
shalom

Now lets explain

• 1st arg- file name

• rest - employee types

https://www.mylinuxplace.com/bash-special-variables/

jobs=($@) # makes an array of all the args
(( jobs_num=$#-1 )) # make len number of args-1,
#because we need to subtract the file name

for job in ${jobs[@]:1:$jobs_num}; do #look all array from 2nd arg (exclude filename) until last
    avg=`grep $job "$1" | ./calc.sh` # grep will only find the job
    # in $1 which is 1st arg which is file name 
    echo "Average salary of $job: $avg"
done