How do I iterate through lines in an external file with shell? [duplicate]

Question

I have one file with a list of names. I need to loop through all names in this file from an external file with a shell script. How can I do that?

Example files:

scripts/names.txt

alison barb charlie david 

scripts/script.sh

NAMES="" #names from names.txt file for NAME in $NAMES; do     echo "$NAME" done 

How can I explode the names.txt file into an array in a separate shell script?

Answer 1

One way would be:

while read NAME do     echo "$NAME" done < names.txt 

EDIT: Note that the loop gets executed in a sub-shell, so any modified variables will be local, except if you declare them with declare outside the loop.

Dennis Williamson is right. Sorry, must have used piped constructs too often and got confused.

Answer 2

You'll be wanting to use the 'read' command

while read name do     echo "$name" done < names.txt 

Note that "$name" is quoted -- if it's not, it will be split using the characters in $IFS as delimiters. This probably won't be noticed if you're just echoing the variable, but if your file contains a list of file names which you want to copy, those will get broken down by $IFS if the variable is unquoted, which is not what you want or expect.

If you want to use Mike Clark's approach (loading into a variable rather than using read), you can do it without the use of cat:

NAMES="$(< scripts/names.txt)" #names from names.txt file for NAME in $NAMES; do     echo "$NAME" done 

The problem with this is that it loads the whole file into $NAMES, when you read it back out, you can either get the whole file (if quoted) or the file broken down by $IFS, if not quoted. By default, this will give you individual words, not individual lines. So if the name "Mary Jane" appeared on a line, you would get "Mary" and "Jane" as two separate names. Using read will get around this... although you could also change the value of $IFS