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corrected misreading of Q2 (thanks Chris, Stéphane)
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Gilles 'SO- stop being evil'
Gilles 'SO- stop being evil'
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Q1: Yes. “Field splitting” and “word splitting” are two terms for the same concept.

Q2: NoYes. If IFS is unset (i.e. after unset IFS), it is equivalent IFS being set to $' \t\n' (a space, a tab and a newline). If IFS is set to an empty value (that's what “null” means here) (i.e. after IFS= or IFS='' or IFS=""), no field splitting is performed at all (and $*, which normally uses the first character of $IFS, uses a space character).

Q3: If you want to have the default IFS behavior, you can use unset IFS. If you want to set IFS explicitly to this default value, you can put the literal characters space, tab, newline in single quotes. In ksh93, bash or zsh, you can use IFS=$' \t\n'. Portably, if you want to avoid having a literal tab character in your source file, you can use

IFS=" $(echo t | tr t \\t)
"

Q4: With IFS set to an empty value, read -r line sets line to the whole line except its terminating newline. With IFS=" ", spaces at the beginning and at the end of the line are trimmed. With the default value of IFS, tabs and spaces are trimmed.

Q1: Yes. “Field splitting” and “word splitting” are two terms for the same concept.

Q2: No. If IFS is unset, it is equivalent IFS being set to $' \t\n' (a space, a tab and a newline). If IFS is set to an empty value (that's what “null” means here), no field splitting is performed at all (and $*, which normally uses the first character of $IFS, uses a space character).

Q3: If you want to have the default IFS behavior, you can use unset IFS. If you want to set IFS explicitly to this default value, you can put the literal characters space, tab, newline in single quotes. In ksh93, bash or zsh, you can use IFS=$' \t\n'. Portably, if you want to avoid having a literal tab character in your source file, you can use

IFS=" $(echo t | tr t \\t)
"

Q4: With IFS set to an empty value, read -r line sets line to the whole line except its terminating newline. With IFS=" ", spaces at the beginning and at the end of the line are trimmed. With the default value of IFS, tabs and spaces are trimmed.

Q1: Yes. “Field splitting” and “word splitting” are two terms for the same concept.

Q2: Yes. If IFS is unset (i.e. after unset IFS), it is equivalent IFS being set to $' \t\n' (a space, a tab and a newline). If IFS is set to an empty value (that's what “null” means here) (i.e. after IFS= or IFS='' or IFS=""), no field splitting is performed at all (and $*, which normally uses the first character of $IFS, uses a space character).

Q3: If you want to have the default IFS behavior, you can use unset IFS. If you want to set IFS explicitly to this default value, you can put the literal characters space, tab, newline in single quotes. In ksh93, bash or zsh, you can use IFS=$' \t\n'. Portably, if you want to avoid having a literal tab character in your source file, you can use

IFS=" $(echo t | tr t \\t)
"

Q4: With IFS set to an empty value, read -r line sets line to the whole line except its terminating newline. With IFS=" ", spaces at the beginning and at the end of the line are trimmed. With the default value of IFS, tabs and spaces are trimmed.

Source Link
Gilles 'SO- stop being evil'
Gilles 'SO- stop being evil'
  • 865.3k
  • 205
  • 1.8k
  • 2.3k

Q1: Yes. “Field splitting” and “word splitting” are two terms for the same concept.

Q2: No. If IFS is unset, it is equivalent IFS being set to $' \t\n' (a space, a tab and a newline). If IFS is set to an empty value (that's what “null” means here), no field splitting is performed at all (and $*, which normally uses the first character of $IFS, uses a space character).

Q3: If you want to have the default IFS behavior, you can use unset IFS. If you want to set IFS explicitly to this default value, you can put the literal characters space, tab, newline in single quotes. In ksh93, bash or zsh, you can use IFS=$' \t\n'. Portably, if you want to avoid having a literal tab character in your source file, you can use

IFS=" $(echo t | tr t \\t)
"

Q4: With IFS set to an empty value, read -r line sets line to the whole line except its terminating newline. With IFS=" ", spaces at the beginning and at the end of the line are trimmed. With the default value of IFS, tabs and spaces are trimmed.