wordfree(3C)
NAME
wordexp, wordfree - perform word expansions
SYNOPSIS
#include <wordexp.h>
int wordexp(const char *words, wordexp_t *pwordexp, int
flags);
void wordfree(wordexp_t *pwordexp);
DESCRIPTION
The wordexp() function performs word expansions, subject to
quoting, and places the list of expanded words into the
structure pointed to by pwordexp.
The wordfree() function frees any memory allocated by wor-
dexp() associated with pwordexp.
words Argument
The words argument is a pointer to a string containing one
or more words to be expanded. The expansions will be the
same as would be performed by the shell if words were the
part of a command line representing the arguments to a util-
ity. Therefore, words must not contain an unquoted NEWLINE
or any of the unquoted shell special characters:
| & ; < >
except in the context of command substitution. It also must
not contain unquoted parentheses or braces, except in the
context of command or variable substitution. If the argument
words contains an unquoted comment character (number sign)
that is the beginning of a token, wordexp() may treat the
comment character as a regular character, or may interpret
it as a comment indicator and ignore the remainder of words.
pwordexp Argument
The structure type wordexp_t is defined in the header
<wordexp.h> and includes at least the following members:
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 stores 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 is a separate word in the
pwordexp->we_wordv list. The words are in order. The first
pointer after the last word pointer will be a null pointer.
It is the caller's responsibility to allocate the storage
pointed to by pwordexp. The wordexp() function allocates
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().
flags Argument
The flags argument is used to control the behavior of wor-
dexp(). 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
will point to pwordexp->we_offs NULL pointers, fol-
lowed by pwordexp->we_wordc word pointers, followed by
a NULL pointer.
WRDE_NOCMD
Fail if command substitution is requested.
WRDE_REUSE
The pwordexp argument was passed to a previous suc-
cessful call to wordexp(), and has not been passed to
wordfree(). The result will be the same as if the
application had called wordfree() and then called wor-
dexp() 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 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 must not set WRDE_APPEND. All subse-
quent calls must set it.
2. All of the calls must set WRDE_DOOFFS, or all must not
set it.
3. After the second and each subsequent call,
pwordexp->we_wordv will 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 will 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 must 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 words contains an unquoted:
NEWLINE | & ; < > ( ) { }
in an inappropriate context, wordexp() will fail, and the
number of expanded words will be zero.
Unless WRDE_SHOWERR is set in flags, wordexp() will 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.
If WRDE_DOOFFS is set, then pwordexp-> we_offs must have the
same value for each wordexp() call and wordfree() call using
a given pwordexp.
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.
RETURN VALUES
On successful completion, wordexp() returns 0.
Otherwise, a non-zero value as described in <wordexp.h> is
returned to indicate an error. If wordexp() returns the
value WRDE_NOSPACE, then pwordexp->we_wordc and
pwordexp->we_wordv will be updated to reflect any words that
were successfully expanded. In other cases, they will not be
modified.
The wordfree() function returns no value.
ERRORS
No errors are defined.
USAGE
This function is intended to be used by an application that
wants to do all of the shell's expansions on a word or words
obtained from a user. For example, if the application
prompts for a filename (or list of filenames) and then uses
wordexp() to process the input, the user could respond with
anything that would be valid as input to the shell.
The WRDE_NOCMD flag is provided for applications that, for
security or other reasons, want to prevent a user from exe-
cuting shell command. Disallowing unquoted shell special
characters also prevents unwanted side effects such as exe-
cuting a command or writing a file.
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| MT-Level | MT-Safe |
|_____________________________|_____________________________|
SEE ALSO
fnmatch(3C), glob(3C), attributes(5)
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