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36 lines
1.7 KiB
Plaintext
36 lines
1.7 KiB
Plaintext
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====== Word splitting ======
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FIXME to be continued!
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Word splitting occurs once any of the following expansions are done (and only then!)
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* [[syntax:pe | Parameter expansion]]
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* [[syntax:expansion:cmdsubst | Command substitution]]
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* [[syntax:expansion:arith | Arithmetic expansion]]
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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**!
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===== Internal Field Separator IFS =====
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The ''IFS'' variable holds the characters that Bash sees as word boundaries in this step. The default contains the characters
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* <space>
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* <tab>
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* <newline>
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These characters are also assumed when IFS is **unset**. When ''IFS'' is **empty** (nullstring), no word splitting is performed at all.
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===== Behaviour =====
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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.
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This doesn't happen when the expansion results were **double-quoted**.
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When a null-string (e.g., something that before expanded to >>nothing<<) is found, it is removed, unless it is quoted (''<nowiki>''</nowiki>'' or ''""'').
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__**Again note:**__ Without any expansion beforehand, Bash won't perform word splitting! In this case, the initial token parsing is solely responsible.
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===== See also =====
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* [[syntax:expansion:intro | Introduction to expansion and substitution]]
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* [[syntax:quoting | Quoting and escaping]]
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* [[http://mywiki.wooledge.org/WordSplitting | WordSplitting]], [[http://mywiki.wooledge.org/IFS | IFS]], and [[http://mywiki.wooledge.org/DontReadLinesWithFor | DontReadLinesWithFor]] - Greg's wiki
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