UNIX for Dummies Questions & Answers

Say I had a text file that contained four columns, like the following:

Mack Christopher:237 Avondale Blvd:970-791-6419:S
Ben Macdonor:30 Dragon Rd:647-288-6395:B

I'm making a loop that will replace the fourth column a line in the file with the contents of a variable 'access', but I have no idea how to do it. I've been trying to use awk, but I don't think I am doing it correctly. Does anyone have any ideas?

Try:

Code:

awk '{ $NF="'$access'"; print; }'  file

I tried running that code and it didn't work for me. the error has something to do with my access variable, which in this case is "Student Access":

awk: { $NF="Student
awk: ^ unterminated string

Try this, be aware of the quotes around the variable:

Code:

awk -v var="$access" '{$NF=var}1' file

Sorry for forgetting to mention that my columns were separated by a colon. So I took the code that you gave me and added an -F and this is what I have so far:

Code:

 awk -F ":" -v var="$access" '{$NF=var}1' file

Two things that I am still having trouble with though.

1) What does the 1 inside the single quotes do as part of awk (I'm trying to understand for future uses).

2) The output for the awk command looks like this"

Mack Christopher 237 Avondale Blvd 970-791-6419 Student Access

Is there a way to keep the colons?

Try this:

Code:

awk -F":" -v var="$access" '{$NF=var}1' OFS=":" file

The 1 means "true" to awk and the default action is to print the current line, similar to:

Code:

{print}

On peut aussi permuter 2 colonnes sous vi, donc interactivement.
Dans ton exemple où le séparateur de colonne est ":"

:%s/\(.*\):\(.*\):\(.*\):\(.*\)/\1:\3:\2:\4/

signifie

: après [esc] indique une action sur le texte
% l'action porte sur l'ensemble du texte
s l'action est une substitution
/ début de description de la ligne
\(.*\) un groupe contenant plusieurs caractères quelconque
: sauf : qui sert de séparateur
/ fin de la ligne et commencement de la description
de la réécriture
\1 recopie le premier groupe
: écrit le nouveau séparateur, ici c'est le même
etc

Hope, it's help you

---------------------------------------------------------
(°> Dhénin Jean-Jacques
/ ) 48, rue de la Justice 78300 Poissy
^^ Jean-Jacques@dhenin.fr