Inserting into a column in file-CodePudding

I have two files and first one is comma separated file with 6 columns and 3rd column is empty in it. 2nd file is a list of urls.

How would i insert all values from 2nd file in 3rd column of first file ?

Content of first file Ex :

apple,fruits,,healthy,240
grapes,fruits,,healthy,80
Noodles,junk,,unhealthy,80

Content of 2nd file:

httpsxhhscom
httpseightcom
httpsxyzjcom

Each files have same number of records and need to be mapped one to one while inserting.ex: 1st row in 2nd file goes 3rd column of 1st file.

CodePudding user response：

You can do it with awk simply by reading the second file into an index array and then updating the 3rd field in file1. For example:

awk -F, -v OFS="," 'FNR==NR {a[  n]=$1; next} m<=n {$3=a[  m]}1' file2 file1

Explanation

the option -F, sets the field separator variable (FS) to ",",
the option -v OFS="," sets the output field separator variable (OFS) to ",",
FNR == NR (first rule condition) - the file record number (FNR - line number per-file) is equal to the total number of records processed (NR) -- only true for the first file processed by awk. FNR is reset to 1 for each file read, NR continues to increment.
If conditon is true, store the url from the first file processed (file2) in the indexed array a[] with indexes 1, 2, 3, .... next skips to the next record (line) at that point.
m <= n second rule condition - this will only be reached when processing the second file (file1). The 3rd field is updaded to the url stored in array a[] in order until the end of the second file or when m > n (if there are more records in the second file than the first)
Note: m and n are simple variables used as counters for the array index. In awk when a variable is encountered before it is initialized or assigned a value, it's value is 0, so n simple sets n = 1 the first time it is used. When m <= n is encountered before m has been incremented, it's value is 0.
1 at the end is just shorthand for the default operation print.

Example Use/Output

With your data in file1 and file2, you would get:

$ awk -F, -v OFS="," 'FNR==NR {a[  n]=$1; next} m<=n {$3=a[  m]}1' file2 file1
apple,fruits,httpsxhhscom,healthy,240
grapes,fruits,httpseightcom,healthy,80
Noodles,junk,httpsxyzjcom,unhealthy,80

To write that out to a file, simply redirect the result to a new file, e.g. > newfile.

CodePudding user response：

If file2 isn't gigantic, might as well pre-read it all :

mawk 'BEGIN {                                 RS="^$"
               getline <ARGV[  _]
     delete __[split ($(ARGV[_  -!  _]=""),__,RS="\n")] 
         FS = \
        OFS = "," } $_=__[NR]' testf2.txt testf1.txt

apple,fruits,httpsxhhscom,healthy,240
grapes,fruits,httpseightcom,healthy,80
Noodles,junk,httpsxyzjcom,unhealthy,80

Tested and confirmed working on gawk 5.1.1, mawk 1.3.4, mawk 1.996, and macos nawk

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