Linux shell script, search by an input string

So, there is a large file where I have to conduct several search using bash shell scripting.
The file is like this:

TITLE and AUTHOR                                                     ETEXT NO.  Aspects of plant life; with special reference to the British flora,      56900  by Robert Lloyd Praeger  The Vicar of Morwenstow, by Sabine Baring-Gould                          56899  [Subtitle: Being a Life of Robert Stephen Hawker, M.A.]  Raamatun tutkisteluja IV, menness� Charles T. Russell                    56898  [Subtitle: Harmagedonin taistelu]  [Language: Finnish]  Raamatun tutkisteluja III, menness� Charles T. Russell                   56897  [Subtitle: Tulkoon valtakuntasi]  [Language: Finnish]  Tom Thatcher's Fortune, by Horatio Alger, Jr.                            56896  A Yankee Flier in the Far East, by Al Avery                              56895  and George Rutherford Montgomery  [Illustrator: Paul Laune]  Nancy Brandon's Mystery, by Lillian Garis                                56894  Nervous Ills, by Boris Sidis                                             56893  [Subtitle: Their Cause and Cure]  Pens�es sans langage, par Francis Picabia                                56892  [Language: French]  Helon's Pilgrimage to Jerusalem, Volume 2 of 2, by Frederick Strauss     56891  [Subtitle: A picture of Judaism, in the century   which preceded the advent of our Savior]  Fra Tommaso Campanella, Vol. 1, di Luigi Amabile                         56890  [Subtitle: la sua congiura, i suoi processi e la sua pazzia]  [Language: Italian]  The Blue Star, by Fletcher Pratt                                         56889  Importanza e risultati degli incrociamenti in avicoltura,                56888  di Teodoro Pascal  [Language: Italian]  The Junior Classics, Volume 3: Tales from Greece and Rome, by Various    56887   ~ ~ ~ ~ Posting Dates for the below eBooks:  1 Mar 2018 to 31 Mar 2018 ~ ~ ~ ~  TITLE and AUTHOR                                                     ETEXT NO.  The American Missionary, Volume 41, No. 1, January, 1887, by Various     56886  Morganin miljoonat, menness� Sven Elvestad                               56885  [Author a.k.a. Stein Riverton]  [Subtitle: Salapoliisiromaani]  [Language: Finnish]  "Trip to the Sunny South" in March, 1885, by L. S. D                     56884  Balaam and His Master, by Joel Chandler Harris                           56883  [Subtitle: and Other Sketches and Stories]  Susien saaliina, menness� Jack London                                    56882  [Language: Finnish]  Forged Egyptian Antiquities, by T. G. Wakeling                           56881  The Secret Doctrine, Vol. 3 of 4, by Helena Petrovna Blavatsky           56880  [Subtitle: Third Edition]  No Posting                                                               56879  First love and other stories, by Iv�n Turg�nieff                         56878

Now I have to search it with etext no, author name and title..
Like If I search by an etext no: like etext 56900: It should return

Aspects of plant life; with special reference to the British flora,      56900

Well I am new to shell scripting. And I can only read the file. With this:

#!/bin/sh read -p 'string to search ' searchstring grep --color searchstring GUTINDEX.ALL | #condition

I don't know what kind of condition I should use to search by author name or etext no....

Welcome to the forum.

Unfortunately, with your above specification, I'm not sure what to do. Is that really a single line data file? What be the record separator? If you "search it with etext no, author name and title", why is the author missing in the sample result? And, what is that sample code supposed to do (after the syntax errors have been corrected)?