How to merge two documents in Bash? - linux

Question

Right now I have a bash shell script that takes the input of a text file with the syntax for example, "Smith, Bob". The end goal is to take the first letter of the first name and append the first 7 characters of the last name. I am currently in a pickle.
echo "Extracting first letter"
cut -d "," -f2 $1 > first.txt
cut -b2 first.txt > second.txt
echo "First letter extracted"
echo "Extracting 7 characters"
cut -d "," -f1 $1 > letters.txt
cat second.txt | tr '[:upper:]' '[:lower:]' > lowernames.txt
I have two files, one with the first letter, the other with the first 7 characters, but can't combine the two. Any suggestions?

Answer 1

Here are three solutions, one using sed, one using awk, and one using python:
Using sed
Here is a sed solution. Using the same test file as sehe:
$ cat file
Smith, Bob
Doe, John
Snow, John
Pattitucci, John
$ sed -E 's/([^,]{1,7})[^,]*,\s*(\S).*/\2\1/' file
BSmith
JDoe
JSnow
JPattitu
How it works
The idea is to capture the first 7 letters of the last name to group 1 and the first letter of the last name to group 2. The regex to do that consists of the following parts:
([^,]{1,7})
This captures up to seven characters of the last name.
`[^,]*,
This matches any characters after the first seven of the last name and the comma which follows.
\s*
This matches any spaces which follow the comma
(\S)
This matches the first character of the first name
.*
This matches any remaining characters of the first name.
Using awk
$ awk -F', *' '{print substr($2,1,1) substr($1,1,7)}' file
BSmith
JDoe
JSnow
JPattitu
How it works
-F', *'
This declares the field separator to be a comma followed by zero or more spaces
substr($1,1,7)
This selects the first seven characters of the last name
substr($2,1,1)
This selects the first character of the first name
Using python
$ python3 -c 'for line in open("file"): last, first=line.strip().split(", "); print(first[:1] + last[:7])'
BSmith
JDoe
JSnow
JPattitu

Answer 2

You can do this without any external process:
while read surname firstname
do
surname="${surname%,}"
echo "${firstname:0:1}${surname:0:7}"
done
See it Live On IdeOne
Input
Smith, Bob
Doe, John
Snow, John
Pattitucci, John
Output
BSmith
JDoe
JSnow
JPattitu

Answer 3

using awk :
awk -F ', ' '{printf("%s%s\n",substr($2,1,1),subsstr($1,1,7))}' file
input:
Smith, Bob
Doe, John
Snow, John
Pattitucci, John
output:
BSmith
JDoe
JSnow
JPattitucci
the input text is splited on ', ' and substr will extract the 1st character of 2nd field