mjhjmtu

Input File My .txt file contains these kind of content :

Tom Thatcher's Fortune, by Horatio Alger, Jr. 56896
Paradise Lost, by John Milton 20

The first string is book name,second is author and the last one is book number. I want to print the whole line when someone search for the book number (if the book number matches).
I'm new to bash scripting.

Something like

grep BOOKNUMBER textfile.txt

should solve this.

If you want to avoid that searching for book number 96 also lists Tom Thatcher's Fortune you can use

grep '[[:space:]]BOOKNUMBER[[:space:]]*$' textfile.txt

instead.

As a script (save as searchbook)

#!/bin/bash

BOOKFILE=/path/to/bookfile.txt

BOOK=$1
if [[ -z "$BOOK" ]]; then 
 echo -n "Booknumber? "
 read BOOK
fi

grep '[[:space:]]'$BOOK'[[:space:]]*$' $BOOKFILE

You can then either run

searchbook BOOKNUMBER

or

searchbook

In the second case you will get prompted for the number.

You can use grep for this:

grep 56896 file.txt

If you wanted to script it, it could be something like this:

#!/bin/bash

inputfile='/path/to/file.txt'

grep "$1" "$inputfile"

Which you would then run like:

$ ./script.sh 56896

To avoid catching book # 196 along with book # 96, I suggest a similar but more terse usage of grep:

grep ' 96$' file.txt

The $ symbol in regular expressions meaning 'the end of the text sample', so it will only match on the correct line.

This can also be put into a script:

#!/bin/bash

grep " $1$" /path/to/file.txt

This can also be done a bit more safely with awk:

awk -v book=96 '$NF == book print' file.txt

To print the lines for which the last word is something, awk comes to mind:

awk '$NF == "123"' # string comparison
awk '$NF == 123' # number comparison, would also match on 0123, 123.0, 1.23e2
awk '$NF == ENVIRON["ENVVAR"]' # number comparison if both $NF and $ENVVAR
 # look like numbers, string otherwise

For awk, those words by default are blank-separated. Depending on the implementation blank may be only space or tab characters, some may include other Unicode blank characters if classified as such in the locale. The busybox awk implementation also includes vertical spacing characters including the carriage return character.

If your file is formatted with MS-DOS line delimiters, that is the CR LF sequence of characters as opposed to just LF, then except with busybox awk, the above won't work. And even with busybox awk, the output lines would still have those problematic control characters that shouldn't be there on Unix.

So you should preprocess the input with dos2unix or d2u to convert the line endings to Unix format.

< file.dos dos2unix | awk '$NF == 123'

Your input file looks like it's made of records that are separated by blank lines. If you want to print the full records for a book number, you could do:

export BOOKNUMBER=123
< file.dos dos2unix | awk -v RS= -F 'n' '
 field[split($1, field, " ")] == ENVIRON["BOOKNUMBER"]'

There, we set the record separator to the empty string to enter the paragraph mode (records separated by blank lines), and the field separator to newline (aka LF) so the first line of each record is in $1 (the first field). We split that first line with the special " " field separator which is the default word splitting into the field array. And then compare the last element of that array (split() returns the number of elements, so field[split()] is the last element) with the content of the $BOOKNUMBER environment variable.