1

data.txt

height= 6'1" age= shoe-size=9.5 sex= M
height= 6'5" age= shoe-size=9.0 sex= M
height= 5'11" age= shoe-size=8.5 sex= F
height= 5'9" age= shoe-size=11.5 sex= M
height= 4'11" age= shoe-size=7.5 sex= F
height= 6'4" age= shoe-size=9.5 sex= M

age.txt

21
23
22
19
34
27

How do I grab the information from the age.txt and place it into data.txt, putting each number following the other into the age portion of data.txt?

Is there a way to do a for loop for the number of lines in my file and then look for 'age' and every time I see age, replace it with the number in age.txt

Expected output

height= 6'1" age=21 shoe-size=9.5 sex= M
height= 6'5" age=23 shoe-size=9.0 sex= M
height= 5'11" age=22 shoe-size=8.5 sex= F
height= 5'9" age=19 shoe-size=11.5 sex= M
height= 4'11" age=34 shoe-size=7.5 sex= F
height= 6'4" age=27 shoe-size=9.5 sex= M
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3 Answers 3

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3

Using bash4 index arrays. 

mapfile -t data < data.txt
mapfile -t age <age.txt

for i in "${!data[@]}"; do echo "${data[$i]//age=/age="${age[$i]}"}"; done

Output is this.

height= 6'1" age=21 shoe-size=9.5 sex= M
height= 6'5" age=23 shoe-size=9.0 sex= M
height= 5'11" age=22 shoe-size=8.5 sex= F
height= 5'9" age=19 shoe-size=11.5 sex= M
height= 4'11" age=34 shoe-size=7.5 sex= F
height= 6'4" age=27 shoe-size=9.5 sex= M

mapfile aka readarray is a bash4+ feature.

The ${!data[@]} means you're looking for the index of an array and ${data[@]} is the array.

Or using while loop and read read, so basically it is just reading the two files inside a while loop.

while IFS= read -r line_in_data <&3
  read -r line_in_age; do
  printf '%s\n' "${line_in_data//age=/age=$line_in_age}"
done 3<data.txt <age.txt

Should print the same output.

height= 6'1" age=21 shoe-size=9.5 sex= M
height= 6'5" age=23 shoe-size=9.0 sex= M
height= 5'11" age=22 shoe-size=8.5 sex= F
height= 5'9" age=19 shoe-size=11.5 sex= M
height= 4'11" age=34 shoe-size=7.5 sex= F
height= 6'4" age=27 shoe-size=9.5 sex= M

POSIX sh solution.

#!/bin/sh

while read -r column1_in_data column2_in_data column3_in_data rest_of_columns_in_data <&3
  read -r line_in_age; do
  printf '%s\n' "$column1_in_data $column2_in_data $column3_in_data$line_in_age $rest_of_columns_in_data"
done 3<data.txt <age.txt

the <&3 is a redirection so the first read will read from FD (file descriptor 3.)

The ${var//search/rep} is a bash specific P.E. (parameter expansion.)

Awk can do better/faster on large set of files/data I believe.

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3 Comments

Thanks! Can you explain what this means: "${!data[@]}"
See: Creating an array from a text file in Bash
@yoyo31 If name is an array variable, expands to the list of array indices (keys) assigned in name. If name is not an array, expands to 0 if name is set and null otherwise. When ‘@’ is used and the expansion appears within double quotes, each key expands to a separate word. From bash documentation.
2

Using awk and getline provides a very simple and efficient solution, e.g.

awk '{getline age < "age.txt"; $3=$3 age}1' data.txt

Above you are simply using getline to read from age.txt into the variable age and then appending age to the 3rd field from data.txt.

Another way so long as "age=" only appears once in the line would be:

awk '{getline age < "age.txt"; sub(/age=/,"age=" age)}1' data.txt

Example Use/Output

You can just copy and middle-mouse paste into an xterm in the directory where your files are located, e.g.

$ awk '{getline age < "age.txt"; $3=$3 age}1' data.txt
height= 6'1" age=21 shoe-size=9.5 sex= M
height= 6'5" age=23 shoe-size=9.0 sex= M
height= 5'11" age=22 shoe-size=8.5 sex= F
height= 5'9" age=19 shoe-size=11.5 sex= M
height= 4'11" age=34 shoe-size=7.5 sex= F
height= 6'4" age=27 shoe-size=9.5 sex= M
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8 Comments

what does the '1' at the end do?
1 is just shorthand for the default rule print :)
Thanks so much David. If I wanted to grab it from a variable instead of a text file, how can I use awk for that? Do I just replace '$3=$3 age' with '$3=$3 $var'?
You would have to pass var in as variable from the shell. You can do that at the beginning with -v varname="$var". However, since awk processes all the records, using getline to read from the age.txt file is probably your best option. (your other option would be to process the age.txt file first and just fill an array with the values and then process data.txt)
Let's say I already had a variable that I grab from, how do I place it into awk? Would it be like this? awk -v '{varname="$var"; $3=$3 varname}1' data.txt and lastly, how do I save that awk line, would I just have to append it to a new text file or can I use the existing one?
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1

You could do it with a bunch of cut and paste and process substitution:

paste -d ' ' \
    <(paste -d'\0'  \
        <(cut -d' ' -f-3 data.txt) \
        age.txt) \
    <(cut -d' ' -f4- data.txt)

The outer paste command uses a blank as the delimiter to paste the output of the inner paste and the outer cut together.

The inner paste uses a null delimiter so there is no blank between age= and the age value.

This being said, the input file format seems inconsistent regarding the spacing around =.

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