Replacing text strings in bash using awk - bash

Question

I have a list of files in bash - file1.txt, file2.txt, file3.txt and I would like to make another list that include this strings without .txt, so
names2 = (file1, file2, file3)
Then, I would like to find these strings in a file and add a before this strings. How to do that please?
My Code:
names = (file1.txt, file2.txt, file3.txt)
for i in "${names[#]}"; do
awk '{ gsub("$i","a-$i") }' f.txt > g.txt
f.txt:
TEXT
\connect{file1}
\begin{file2}
\connect{file3}
TEXT
75
Desired output g.txt
TEXT
\connect{a-file1}
\begin{a-file2}
\connect{a-file3}
TEXT
75

Answer 1

With sed+printf:
$ names=(file1 file2 file3) # Declare array
$ printf 's/%s/a-&/g\n' "${names[#]}" # Generate sed replacement script
s/file1/a-&/g
s/file2/a-&/g
s/file3/a-&/g
$ sed -f <(printf 's/%s/a-&/g\n' "${names[#]}") f.txt
TEXT
\connect{a-file1}
\begin{a-file2}
\connect{a-file3}
TEXT
75
If your array contains .txt suffix, use this:
$ names=(file1.txt file2.txt file3.txt) # Declare array
$ printf 's/%s/a-&/g\n' "${names[#]%.txt}" # Generate sed replacement script
s/file1/a-&/g
s/file2/a-&/g
s/file3/a-&/g
$ sed -f <(printf 's/%s/a-&/g\n' "${names[#]%.txt}") f.txt
TEXT
\connect{a-file1}
\begin{a-file2}
\connect{a-file3}
TEXT
75
If the files list contains the names which have overlapping string, you can use the word boundaries (\<,\>) to handle this.
e.g.
$ cat f.txt
TEXT
\connect{file1}
\begin{file2}
\connect{file3file2}
TEXT
75
$ names=(file1.txt file2.txt file3file2.txt) # Declare array
$ printf 's/\<%s\>/a-&/g\n' "${names[#]%.txt}" # Generate sed replacement script
s/\<file1\>/a-&/g
s/\<file2\>/a-&/g
s/\<file3file2\>/a-&/g
$ sed -f <(printf 's/\<%s\>/a-&/g\n' "${names[#]%.txt}") f.txt
TEXT
\connect{a-file1}
\begin{a-file2}
\connect{a-file3file2}
TEXT
75

Answer 2

Could you please try following.
Variable with values in shell:
string="file1.txt, file2.txt, file3.txt"
Creating a shell array as follows:
IFS=', ' read -r -a array <<< "$string"
OR if you want to stick with your way of defining array then do like:
array=(file1.txt file2.txt file3.txt)
Passing above shell created array to awk and reading Input_file for doing the final operations.
awk -v arr="${array[*]}" '
BEGIN{
FS=OFS="{"
num=split(arr,array," ")
for(i=1;i<=num;i++){
sub(/\.txt/,"",array[i])
array1[array[i]"}"]
}
}
$2 in array1{
$2="a-"$2
}
1
' Input_file
Explanation: Adding explanation of above code here.
awk -v arr="${array[*]}" ' ##Creating a variable named arr whose value is all elements of array(shell array).
BEGIN{ ##Starting BEGIN section of awk code here.
FS=OFS="{" ##Setting FS and OFS as { here.
num=split(arr,array," ") ##Splitting arr variable into array named array with delimiter space and its length is stored in num variable.
for(i=1;i<=num;i++){ ##Starting for loop from i=1 to till value of variable num.
sub(/\.txt/,"",array[i]) ##Using sub to substitute .txt with NULL in array value whose index is variable named i.
array1[array[i]"}"] ##Creating an array1 whose index is array[i] value with } in it.
} ##Closing for loop here.
} ##Closing BEGIN section of code here.
$2 in array1{ ##Checking condition if $2 of current line is present in array named array1 then do following.
$2="a-"$2 ##Adding string a- with value of $2.
} ##Closing BLOCK for condition here.
1 ##Mentioning 1 will print edited/non-edited line of Input_file.
' Input_file ##Mentioning Input_file name here.