The following few threads on this site and StackOverflow were helpful for understanding how IFS works: What is IFS in context of for looping? How to loop over the lines of a file Bash, read line b...

Jul 20, 2016 · The default value for IFS consists of whitespace characters (to be precise: space, tab and newline). Each character can be a word boundary. So, with the default value of IFS, the loop above will print: Word: foo:bar Word: baz Word: rab In other words, the shell thinks that whitespace is a word boundary. Now, try setting IFS=: before executing ...

Feb 20, 2023 · The default value of IFS is space, tab and newline, so if foo prints out two lines hello world and howdy then the loop body is executed with x=hello, then x=world and x=howdy. If IFS is explicitly changed to contain a newline only, then the loop is …

Jun 12, 2015 · IFS is the Input Field Separator, which means the string read will be split based on the characters in IFS. On a command line, IFS is normally any whitespace characters, that's why the command line splits at spaces. Doing something like VAR=value command means "modify the environment of command so that VAR will have the value value".

Oct 26, 2018 · ifs=' ' which is equivalent but harder to read. BTW: This extension already has passed the POSIX standard commitee, but it is scheduled for SUSv8 that is expected to appear not before the year 2020 because we first need to work on our lag behind the current list of bugs.

Aug 17, 2011 · The IFS= read -r line sets the environment variable IFS (to an empty value) specifically for the execution of read. This is an instance of the general simple command syntax: a (possibly empty) sequence of variable assignments followed by a command name and its arguments (also, you can throw in redirections at any point).

Oct 10, 2017 · In old versions of bash you had to quote variables after <<<.That was fixed in 4.4. In older versions, the variable would be split on IFS and the resulting words joined on space before being stored in the temporary file that makes up that <<< redirection.

Mar 19, 2021 · An alternative way of doing this, suggested by LL3 in comments (now deleted), relies on prefixing the unset command by :, a built-in utility that does nothing, effectively commenting out the unset, when it's not needed:

Any character in IFS that is not IFS whitespace, along with any adjacent IFS whitespace characters, delimits a field. A sequence of IFS whitespace characters is also treated as a delimiter. It means that IFS whitespace (space, tab and newline) is …

Nov 10, 2021 · IFS= and IFS=$'\n' are identical when it comes to read (assuming the read delimiter is not changed from the default), since the only difference is whether a newline inside a line separates words, but a newline never appears inside a line. read and read -d $'\n' are identical since $'\n' (newline) is the default delimiter.