mirror of
https://github.com/flokoe/bash-hackers-wiki.git
synced 2024-11-01 14:53:06 +01:00
36 lines
1.7 KiB
Plaintext
36 lines
1.7 KiB
Plaintext
====== Word splitting ======
|
|
|
|
FIXME to be continued!
|
|
|
|
Word splitting occurs once any of the following expansions are done (and only then!)
|
|
* [[syntax:pe | Parameter expansion]]
|
|
* [[syntax:expansion:cmdsubst | Command substitution]]
|
|
* [[syntax:expansion:arith | Arithmetic expansion]]
|
|
Bash will scan the results of these expansions for special ''IFS'' characters that mark word boundaries. This is only done on results that are **not double-quoted**!
|
|
|
|
===== Internal Field Separator IFS =====
|
|
|
|
The ''IFS'' variable holds the characters that Bash sees as word boundaries in this step. The default contains the characters
|
|
* <space>
|
|
* <tab>
|
|
* <newline>
|
|
These characters are also assumed when IFS is **unset**. When ''IFS'' is **empty** (nullstring), no word splitting is performed at all.
|
|
|
|
|
|
|
|
|
|
===== Behaviour =====
|
|
|
|
The results of the expansions mentioned above are scanned for ''IFS''-characters. If **one or more** (in a sequence) of them is found, the expansion result is split at these positions into multiple words.
|
|
|
|
This doesn't happen when the expansion results were **double-quoted**.
|
|
|
|
When a null-string (e.g., something that before expanded to >>nothing<<) is found, it is removed, unless it is quoted (''<nowiki>''</nowiki>'' or ''""'').
|
|
|
|
__**Again note:**__ Without any expansion beforehand, Bash won't perform word splitting! In this case, the initial token parsing is solely responsible.
|
|
|
|
|
|
===== See also =====
|
|
* [[syntax:expansion:intro | Introduction to expansion and substitution]]
|
|
* [[syntax:quoting | Quoting and escaping]]
|
|
* [[http://mywiki.wooledge.org/WordSplitting | WordSplitting]], [[http://mywiki.wooledge.org/IFS | IFS]], and [[http://mywiki.wooledge.org/DontReadLinesWithFor | DontReadLinesWithFor]] - Greg's wiki |