All the functions, constants and data types for word expansion are
declared in the header file wordexp.h.
Word expansion produces a vector of words (strings). To return this
vector, wordexp uses a special data type, wordexp_t, which
is a structure. You pass wordexp the address of the structure,
and it fills in the structure's fields to tell you about the results.
— Data Type: wordexp_t
This data type holds a pointer to a word vector. More precisely, it
records both the address of the word vector and its size.
The number of elements in the vector.
The address of the vector. This field has type char **.
The offset of the first real element of the vector, from its nominal
address in the we_wordv field. Unlike the other fields, this
is always an input to wordexp, rather than an output from it.
If you use a nonzero offset, then that many elements at the beginning of
the vector are left empty. (The wordexp function fills them with
The we_offs field is meaningful only if you use the
WRDE_DOOFFS flag. Otherwise, the offset is always zero
regardless of what is in this field, and the first real element comes at
the beginning of the vector.
— Function: int wordexp (const char *words, wordexp_t *word-vector-ptr, int flags)
Perform word expansion on the string words, putting the result in
a newly allocated vector, and store the size and address of this vector
into *word-vector-ptr. The argument flags is a
combination of bit flags; see Flags for Wordexp, for details of
You shouldn't use any of the characters `|&;<>' in the string
words unless they are quoted; likewise for newline. If you use
these characters unquoted, you will get the WRDE_BADCHAR error
code. Don't use parentheses or braces unless they are quoted or part of
a word expansion construct. If you use quotation characters `'"`',
they should come in pairs that balance.
The results of word expansion are a sequence of words. The function
wordexp allocates a string for each resulting word, then
allocates a vector of type char ** to store the addresses of
these strings. The last element of the vector is a null pointer.
This vector is called the word vector.
To return this vector, wordexp stores both its address and its
length (number of elements, not counting the terminating null pointer)
If wordexp succeeds, it returns 0. Otherwise, it returns one
of these error codes:
The input string words contains an unquoted invalid character such
The input string refers to an undefined shell variable, and you used the flag
WRDE_UNDEF to forbid such references.
The input string uses command substitution, and you used the flag
WRDE_NOCMD to forbid command substitution.
It was impossible to allocate memory to hold the result. In this case,
wordexp can store part of the results—as much as it could
allocate room for.
There was a syntax error in the input string. For example, an unmatched
quoting character is a syntax error.