Unix Adding grep Option to Bash Script

Question

In a bash script I am working on I need to add a grep option to be accepted at the command line to only read words from a file that match a pattern. The user is prompted to enter books, authors, publishers, and publish years, and the list is stored in a file books in book1~author1~pub1~date1 format, with each set on a separate line. If "print" is passed at the command line (bookinfo print), the file "books" content is put in a book_print file in Book: book1 (\n) Author: author1 ect. format. What I am trying to do is add a grep option so that when a string is specified at the command line with the -f option, only lines in the "books" file that include that pattern are put in the "book_print" file. For example, if the command is "bookinfo -f "author2"", only lines in "books" that include author2 will be put in the book_print file. (bookinfo is the name of the script)

Here is what I have so far. I started the -f option code but don't know where to go from here.

#!/bin/bash
n=${1:-1}
#while getopts f name
#do
#       case $name in
#               f)dopt=1;;
#               *) echo "Invalid arg";;
#       esac
#done
if [[ $1 == "print" ]]
then
    printf "Booktitle: \t\t %s\n" `awk -F '~' '{print $1}' books` >> book_print
    printf "Author(s): \t\t %s\n" `awk -F '~' '{print $2}' books` >> book_print
    printf "Publisher: \t\t %s\n" `awk -F '~' '{print $3}' books`  >> book_print
    printf "Year of Publication: \t %s\n" `awk -F '~' '{print $4}' books` >> book_print
else
    for ((i = 1; i < n + 1; i++))
    do
        echo -n "Booktitle: " 
        read  b
        book=$b
        echo -n $book >> books
        echo -n "~" >> books
        echo -n "Author(s): "
        read a
        author=$a
        echo -n $author >> books
        echo -n "~" >> books
        echo -n "Publisher: "
        read  p
        publisher=$p
        echo -n $publisher >> books
        echo -n "~" >> books
        echo -n "Year of publication: "
        read y
        year=$y
        echo $year >> books
    done
fi

EDIT - I changed the while loop code to the following:

while getops ":f" opt;
do
    case $opt in
        f)
            grep "$OPTARG" books
            ;;
        *)
            echo "Invalid argument."
            ;;
     esac
done

My books file contains the lines A~B~C~D and E~F~G~H. When I run the command ./bookinfo -f "A", I am shown the entire books file rather than just the line that contains A.

ffledgling · Accepted Answer · 2016-02-28 00:40:38Z

2

Seems like you were headed in the right direction, here's what you need:

#!/bin/bash

while getopts "f:" opt;
do
  case $opt in
    f)
      echo "Found pattern: $OPTARG"
      ;;
    *)
      echo "Wrong arg"
      # Call the usage function here
  esac
done

You might want to read up on this getops tutorial for further understanding of how getops works.

edited Feb 28, 2016 at 0:40

answered Feb 28, 2016 at 0:35

ffledgling

12.3k8 gold badges52 silver badges70 bronze badges

Sign up to request clarification or add additional context in comments.

6 Comments

glenn jackman Over a year ago

Any time I use getopts (which is a lot), I add a -h option to document what the valid options are.

ffledgling Over a year ago

@glennjackman Yes, that's good practice, just not what was asked in the question. :)

tfreiner Over a year ago

Thanks for your help, I changed my while loop and edited the OP with the change. My script is still not working as it should though and I think it may be a result of my grep command.

ffledgling Over a year ago

@tfreiner if you could add a few sample test cases of the book files and what the expected output would be for a specific call to your script, then I might be able to help more.

tfreiner Over a year ago

I figured it out. I was using grep $OPTARG when I should have been using grep $2. Thanks for your help!

|

2 revs · Accepted Answer · 2016-02-28 02:05:57Z

Not an answer, but a quick rewrite to make your code a little tighter:

print() {
    # doing this in a single awk command is much more efficient
    # the default search pattern is "non-empty line"
    awk -F '~' -v pattern="${1:-.}" '
        $0 ~ pattern {
            printf "Booktitle: \t\t %s\n", $1
            printf "Author(s): \t\t %s\n", $2
            printf "Publisher: \t\t %s\n", $3
            printf "Year of Publication: \t %s\n", $4
        }
    ' books >> book_print
}

populate() {
    while true; do
        # use read -p to incorporate the prompt, 
        # and just use one variable per item
        read -p "Booktitle (blank to quit): " book
        [[ -z "$book" ]] && break
        reap -p "Author(s): " author
        read -p "Publisher: " publisher
        read -p "Year of publication: " year
        # critically important to quote the variables here:
        printf "%s~%s~%s~%s\n" "$book" "$author" "$publisher" "$year"
    done >> books
}

# magic getopts here to set the search pattern, say in $search variable,
# and a flag to indicate print versus populate

if [[ "$do_search" -eq 1 ]]; then
    print "$search"
else
    populate
done

Collectives™ on Stack Overflow

Unix Adding grep Option to Bash Script

2 Answers 2

6 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

6 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related