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   wordexp.3p    ( 3 )

выполнять расширения слов (perform word expansions)

Описание (Description)

The wordexp() function shall perform word expansions as described
       in the Shell and Utilities volume of POSIX.1‐2017, Section 2.6,
       Word Expansions, subject to quoting as described in the Shell and
       Utilities volume of POSIX.1‐2017, Section 2.2, Quoting, and place
       the list of expanded words into the structure pointed to by
       pwordexp.

The words argument is a pointer to a string containing one or more words to be expanded. The expansions shall be the same as would be performed by the command line interpreter if words were the part of a command line representing the arguments to a utility. Therefore, the application shall ensure that words does not contain an unquoted <newline> character or any of the unquoted shell special characters '|', '&', ';', '<', '>' except in the context of command substitution as specified in the Shell and Utilities volume of POSIX.1‐2017, Section 2.6.3, Command Substitution. It also shall not contain unquoted parentheses or braces, except in the context of command or variable substitution. The application shall ensure that every member of words which it expects to have expanded by wordexp() does not contain an unquoted initial comment character. The application shall also ensure that any words which it intends to be ignored (because they begin or continue a comment) are deleted from words. If the argument words contains an unquoted comment character (<number-sign>) that is the beginning of a token, wordexp() shall either treat the comment character as a regular character, or interpret it as a comment indicator and ignore the remainder of words.

The structure type wordexp_t is defined in the <wordexp.h> header and includes at least the following members:

┌──────────────┬──────────────┬────────────────────────────────────┐ │Member Type Member Name Description │ ├──────────────┼──────────────┼────────────────────────────────────┤ │size_t we_wordc │ Count of words matched by words. │ │char ** we_wordv │ Pointer to list of expanded words. │ │size_t we_offs │ Slots to reserve at the beginning │ │ │ │ of pwordexp->we_wordv. │ └──────────────┴──────────────┴────────────────────────────────────┘ The wordexp() function shall store the number of generated words into pwordexp->we_wordc and a pointer to a list of pointers to words in pwordexp->we_wordv. Each individual field created during field splitting (see the Shell and Utilities volume of POSIX.1‐2017, Section 2.6.5, Field Splitting) or pathname expansion (see the Shell and Utilities volume of POSIX.1‐2017, Section 2.6.6, Pathname Expansion) shall be a separate word in the pwordexp->we_wordv list. The words shall be in order as described in the Shell and Utilities volume of POSIX.1‐2017, Section 2.6, Word Expansions. The first pointer after the last word pointer shall be a null pointer. The expansion of special parameters described in the Shell and Utilities volume of POSIX.1‐2017, Section 2.5.2, Special Parameters is unspecified.

It is the caller's responsibility to allocate the storage pointed to by pwordexp. The wordexp() function shall allocate other space as needed, including memory pointed to by pwordexp->we_wordv. The wordfree() function frees any memory associated with pwordexp from a previous call to wordexp().

The flags argument is used to control the behavior of wordexp(). The value of flags is the bitwise-inclusive OR of zero or more of the following constants, which are defined in <wordexp.h>:

WRDE_APPEND Append words generated to the ones from a previous call to wordexp().

WRDE_DOOFFS Make use of pwordexp->we_offs. If this flag is set, pwordexp->we_offs is used to specify how many null pointers to add to the beginning of pwordexp->we_wordv. In other words, pwordexp->we_wordv shall point to pwordexp->we_offs null pointers, followed by pwordexp->we_wordc word pointers, followed by a null pointer.

WRDE_NOCMD If the implementation supports the utilities defined in the Shell and Utilities volume of POSIX.1‐2017, fail if command substitution, as specified in the Shell and Utilities volume of POSIX.1‐2017, Section 2.6.3, Command Substitution, is requested.

WRDE_REUSE The pwordexp argument was passed to a previous successful call to wordexp(), and has not been passed to wordfree(). The result shall be the same as if the application had called wordfree() and then called wordexp() without WRDE_REUSE.

WRDE_SHOWERR Do not redirect stderr to /dev/null.

WRDE_UNDEF Report error on an attempt to expand an undefined shell variable.

The WRDE_APPEND flag can be used to append a new set of words to those generated by a previous call to wordexp(). The following rules apply to applications when two or more calls to wordexp() are made with the same value of pwordexp and without intervening calls to wordfree():

1. The first such call shall not set WRDE_APPEND. All subsequent calls shall set it.

2. All of the calls shall set WRDE_DOOFFS, or all shall not set it.

3. After the second and each subsequent call, pwordexp->we_wordv shall point to a list containing the following:

a. Zero or more null pointers, as specified by WRDE_DOOFFS and pwordexp->we_offs

b. Pointers to the words that were in the pwordexp->we_wordv list before the call, in the same order as before

c. Pointers to the new words generated by the latest call, in the specified order

4. The count returned in pwordexp->we_wordc shall be the total number of words from all of the calls.

5. The application can change any of the fields after a call to wordexp(), but if it does it shall reset them to the original value before a subsequent call, using the same pwordexp value, to wordfree() or wordexp() with the WRDE_APPEND or WRDE_REUSE flag.

If the implementation supports the utilities defined in the Shell and Utilities volume of POSIX.1‐2017, and words contains an unquoted character—<newline>, '|', '&', ';', '<', '>', '(', ')', '{', '}'—in an inappropriate context, wordexp() shall fail, and the number of expanded words shall be 0.

Unless WRDE_SHOWERR is set in flags, wordexp() shall redirect stderr to /dev/null for any utilities executed as a result of command substitution while expanding words. If WRDE_SHOWERR is set, wordexp() may write messages to stderr if syntax errors are detected while expanding words, unless the stderr stream has wide orientation in which case the behavior is undefined. It is unspecified whether any write errors encountered while outputting such messages will affect the stderr error indicator or the value of errno.

The application shall ensure that if WRDE_DOOFFS is set, then pwordexp->we_offs has the same value for each wordexp() call and wordfree() call using a given pwordexp.

The results are unspecified if WRDE_APPEND and WRDE_REUSE are both specified.

The following constants are defined as error return values:

WRDE_BADCHAR One of the unquoted characters—<newline>, '|', '&', ';', '<', '>', '(', ')', '{', '}'—appears in words in an inappropriate context.

WRDE_BADVAL Reference to undefined shell variable when WRDE_UNDEF is set in flags.

WRDE_CMDSUB Command substitution requested when WRDE_NOCMD was set in flags.

WRDE_NOSPACE Attempt to allocate memory failed.

WRDE_SYNTAX Shell syntax error, such as unbalanced parentheses or unterminated string.