Change output of only the first line in bash script

Question

Here is my source :

TABLE;APGFPOLI;

And here is the output that i want :

01 APGFPOLI.

So what i am trying to do is remove "TABLE" and add 01 before "APGFPOLI". I need to do it for the first line only. So i tried to do :

    #!/bin/bash

#Fichier Source
fichier="APGFPOLI.des.txt"

champAdd="05 "

if [[ -f "$fichier" ]]
then
    
    # read it
    sed -i '1 s/TABLE//' $fichier |sed -i 's/CHAR/PIC X/' $fichier | sed -E '/Numérique/s/;Numérique\s+([^;]*)/;PIC 9(\1)/' $fichier | while IFS=';' read -r nomChamp format libelle
    do
        echo \* $libelle
        echo $champAdd $nomChamp $format.
    done > test.txt
fi

As you can see, my first sed is supposed to remove TABLE but it dont work. i also do a echo for my others line but i'd like to echo this specific first line too.

Here is the output my bash gives me :

  *
05 TABLE APGFPOLI.

Here is my full source if it helps :

TABLE;APGFPOLI;
Contrat;CHAR(16);Numéro du contrat
Libelle;CHAR(30);Libellé du contrat
DtCreation;CHAR(8);Date de création
DtMaj;CHAR(8);Date de dernière MAJ
DtEffet;CHAR(8);Date d'effet adhésion
MotifAdh;CHAR(2);Motif d'adhésion
DtRadiation;CHAR(8);Date de radiation
DtEnrRad;CHAR(8);Date enregistrement radiat
MotifRad;CHAR(2);Motif de radiation
MtPrime;Numérique 8.2;Montant prime d'origine
DtEffetSusp;CHAR(8);Date d'effet de suspension
DtFinSusp;CHAR(8);Date de fin de suspension
MotifSusp;CHAR(2);Motif de suspension
DestBord;CHAR(1);Destinataire du bordereau
CdDest;CHAR(5);Code du destinataire
NivRupBord;CHAR(1);Niveau rupture bordereau
BordCETIP;CHAR(1);Bordereau CTIP
EnvBordNom;CHAR(1);Envoi bordereau nominatif
Indice;CHAR(2);Indice appliqué
Echeance;CHAR(2);Echéance de l'indice (MM)
Effectif;CHAR(5);Effectif
CdRegr;CHAR(3);Code regroupement 1
CdGroupe;CHAR(3);Code regroupement 2
Periodicite;CHAR(1);Périodicité
Terme;CHAR(1);Terme
Produit;CHAR(6);Code produit affecté
Inspecteur;CHAR(5);Inspecteur
CleInsp;CHAR(1);Clé inspecteur
Filler;CHAR(6);Filler

It doesn't make sense to add the flag -i to the command sed and to give the name of a file as argument when you are reading the input from the standard input stream with the operator | in bash. — Pierre François
– Pierre François, Commented Dec 16, 2021 at 10:41
for the moment i do that for one file only but, i'll need to do it for a whole directory of files. that's why — Youssef Hammouma
– Youssef Hammouma, Commented Dec 16, 2021 at 10:43
@YoussefHammouma It doesn't matter whether you're operating on one file or many; sed -i doesn't make any sense in a pipeline. The point of a pipeline is to pass the output from one command to the input of another, but sed -i doesn't produce any output, or read any input. You need to either do the edit with a single sed -i command (no pipe, no read, no echo, etc), or make a shell loop over the files (something like for fichier in *.des.txt; do ...) and use sed without the -i (and only pass the file to the first sed command, so the others read from the pipe, not the file). — Gordon Davisson
– Gordon Davisson, Commented Dec 16, 2021 at 10:52
For #!/bin/bash to do anything useful, the characters # and ! need to be literally the first two bytes of the file. The indentation you show in your question changes this line into just a comment and no longer a valid shebang — tripleee
– tripleee, Commented Dec 16, 2021 at 10:53

tripleee · Accepted Answer · 2021-12-16 11:05:01Z

3

You generally don't want to run sed -i on the same file more than once.

Your entire task can be rephrased into just

sed -i '1s/TABLE/01 /' APGFPOLI.des.txt

If the replacement string should come from a shell variable, you need to use double quotes instead of single:

replacement="05"
sed -i "1s/TABLE/$replacement /" APGFPOLI.des.txt

If you want to keep your other tasks (which are not documented in the question) you can easily merge them into the same script. Remember, sed is a scripting language; you can feed in arbitrarily complex scripts (and some crazy people have even implemented desk calculators and Game of Life in sed scripts).

sed -i -E -e '1 s/TABLE/01 /' -e 's/CHAR/PIC X/' \
          -e '/Numérique/s/;Numérique\s+([^;]*)/;PIC 9(\1)/' APGFPOLI.des.txt

If after this you want to pull out the result and display it with some decorations, I would add a second sed script without -i so that it displays the output on standard output without modifying the file.

sed '1s/\([^;]*\);\([^;]*\);\([^;]*\);.*/* \3\n05 \2 \1/;q'  APGFPOLI.des.txt

edited Dec 16, 2021 at 11:05

answered Dec 16, 2021 at 10:51

tripleee

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6 Comments

Youssef Hammouma Over a year ago

Great, thank you so much. But now with the "echoes" that i put in the shell i have this output : "05 01 APGFPOLI." . Is there a way to echo my first line without the "05" unlike all the other lines ?

tripleee Over a year ago

I would just run another sed to pull out the first line and add the decorations you want around it to standard output. See updated answer with a rough sketch now (hope I transcribed your fields correctly).

Youssef Hammouma Over a year ago

I think that i did full bullsh*t. I saw that sed actually edit my source file. I do not want that, i want to keep my source like that and create a target file with the modifications i did. I am so lost, how can i do that i never tought that sed edit the source file :(

tripleee Over a year ago

Remove the -i option if you don't want to write the changes back to the input file. Going forward, probably spend more time on explaining your actual requirements.

Youssef Hammouma Over a year ago

Ok but why removing the -i option removed the changes in the output file ? Because i removed all the -i so i can keep my original source. But now when i cat my output file there is no changes on it

|

Pierre François · Accepted Answer · 2021-12-16 10:51:56Z

1

For removing TABLE; from the first line and to prepend 01 , you just have to do:

fichier="APGFPOLI.des.txt"
sed -i '1s/^TABLE;/01 /' "$fichier"

When you ask something in SO, it is advisable to remove the part of the code that is not relevant to your problem, like the command sed -i 's/CHAR/PIC X/' $fichier and so on.

answered Dec 16, 2021 at 10:51

Pierre François

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