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
wordexp uses a special data type,
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.
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
- The offset of the first real element of the vector, from its nominal address in the
we_wordvfield. 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
wordexpfunction fills them with null pointers.)
we_offsfield is meaningful only if you use the
WRDE_DOOFFSflag. 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.
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 the flags.
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_BADCHARerror 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
wordexpallocates 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,
wordexpstores both its address and its length (number of elements, not counting the terminating null pointer) into
wordexpsucceeds, it returns 0. Otherwise, it returns one of these error codes:
- The input string words contains an unquoted invalid character such as ‘|’.
- The input string refers to an undefined shell variable, and you used the flag
WRDE_UNDEFto forbid such references.
- The input string uses command substitution, and you used the flag
WRDE_NOCMDto forbid command substitution.
- It was impossible to allocate memory to hold the result. In this case,
wordexpcan 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.