.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved .TH "WORDEXP" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual" .\" wordexp .SH NAME wordexp, wordfree \- perform word expansions .SH SYNOPSIS .LP \fB#include .br .sp int wordexp(const char *restrict\fP \fIwords\fP\fB, wordexp_t *restrict\fP \fIpwordexp\fP\fB, .br \ \ \ \ \ \ int\fP \fIflags\fP\fB); .br void wordfree(wordexp_t *\fP\fIpwordexp\fP\fB); .br \fP .SH DESCRIPTION .LP The \fIwordexp\fP() function shall perform word expansions as described in the Shell and Utilities volume of IEEE\ Std\ 1003.1-2001, Section 2.6, Word Expansions, subject to quoting as in the Shell and Utilities volume of IEEE\ Std\ 1003.1-2001, Section 2.2, Quoting, and place the list of expanded words into the structure pointed to by \fIpwordexp\fP. .LP The \fIwords\fP 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 \fIwords\fP were the part of a command line representing the arguments to a utility. Therefore, the application shall ensure that \fIwords\fP does not contain an unquoted or any of the unquoted shell special characters \fB'|'\fP , \fB'&'\fP , \fB';'\fP , \fB'<'\fP , \fB'>'\fP except in the context of command substitution as specified in the Shell and Utilities volume of IEEE\ Std\ 1003.1-2001, 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 \fIwords\fP which it expects to have expanded by \fIwordexp\fP() 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 \fIwords\fP. If the argument \fIwords\fP contains an unquoted comment character (number sign) that is the beginning of a token, \fIwordexp\fP() shall either treat the comment character as a regular character, or interpret it as a comment indicator and ignore the remainder of \fIwords\fP. .LP The structure type \fBwordexp_t\fP is defined in the \fI\fP header and includes at least the following members: .TS C center; l1 l1 lw(40). \fBMember Type\fP \fBMember Name\fP T{ .na \fBDescription\fP .ad T} \fBsize_t\fP \fIwe_wordc\fP T{ .na Count of words matched by \fIwords\fP. .ad T} \fBchar **\fP \fIwe_wordv\fP T{ .na Pointer to list of expanded words. .ad T} \fBsize_t\fP \fIwe_offs\fP T{ .na Slots to reserve at the beginning of \fIpwordexp\fP->\fIwe_wordv\fP. .ad T} .TE .LP The \fIwordexp\fP() function shall store the number of generated words into \fIpwordexp\fP->\fIwe_wordc\fP and a pointer to a list of pointers to words in \fIpwordexp\fP->\fIwe_wordv\fP. Each individual field created during field splitting (see the Shell and Utilities volume of IEEE\ Std\ 1003.1-2001, Section 2.6.5, Field Splitting) or pathname expansion (see the Shell and Utilities volume of IEEE\ Std\ 1003.1-2001, Section 2.6.6, Pathname Expansion) shall be a separate word in the \fIpwordexp\fP->\fIwe_wordv\fP list. The words shall be in order as described in the Shell and Utilities volume of IEEE\ Std\ 1003.1-2001, 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 IEEE\ Std\ 1003.1-2001, Section 2.5.2, Special Parameters is unspecified. .LP It is the caller's responsibility to allocate the storage pointed to by \fIpwordexp\fP. The \fIwordexp\fP() function shall allocate other space as needed, including memory pointed to by \fIpwordexp\fP->\fIwe_wordv\fP. The \fIwordfree\fP() function frees any memory associated with \fIpwordexp\fP from a previous call to \fIwordexp\fP(). .LP The \fIflags\fP argument is used to control the behavior of \fIwordexp\fP(). The value of \fIflags\fP is the bitwise-inclusive OR of zero or more of the following constants, which are defined in \fI\fP: .TP 7 WRDE_APPEND Append words generated to the ones from a previous call to \fIwordexp\fP(). .TP 7 WRDE_DOOFFS Make use of \fIpwordexp\fP->\fIwe_offs\fP. If this flag is set, \fIpwordexp\fP->\fIwe_offs\fP is used to specify how many null pointers to add to the beginning of \fIpwordexp\fP->\fIwe_wordv\fP. In other words, \fIpwordexp\fP->\fIwe_wordv\fP shall point to \fIpwordexp\fP->\fIwe_offs\fP null pointers, followed by \fIpwordexp\fP->\fIwe_wordc\fP word pointers, followed by a null pointer. .TP 7 WRDE_NOCMD If the implementation supports the utilities defined in the Shell and Utilities volume of IEEE\ Std\ 1003.1-2001, fail if command substitution, as specified in the Shell and Utilities volume of IEEE\ Std\ 1003.1-2001, Section 2.6.3, Command Substitution, is requested. .TP 7 WRDE_REUSE The \fIpwordexp\fP argument was passed to a previous successful call to \fIwordexp\fP(), and has not been passed to \fIwordfree\fP(). The result shall be the same as if the application had called \fIwordfree\fP() and then called \fIwordexp\fP() without WRDE_REUSE. .TP 7 WRDE_SHOWERR Do not redirect \fIstderr\fP to \fB/dev/null\fP. .TP 7 WRDE_UNDEF Report error on an attempt to expand an undefined shell variable. .sp .LP The WRDE_APPEND flag can be used to append a new set of words to those generated by a previous call to \fIwordexp\fP(). The following rules apply to applications when two or more calls to \fIwordexp\fP() are made with the same value of \fIpwordexp\fP and without intervening calls to \fIwordfree\fP(): .IP " 1." 4 The first such call shall not set WRDE_APPEND. All subsequent calls shall set it. .LP .IP " 2." 4 All of the calls shall set WRDE_DOOFFS, or all shall not set it. .LP .IP " 3." 4 After the second and each subsequent call, \fIpwordexp\fP->\fIwe_wordv\fP shall point to a list containing the following: .RS .IP " a." 4 Zero or more null pointers, as specified by WRDE_DOOFFS and \fIpwordexp\fP->\fIwe_offs\fP .LP .IP " b." 4 Pointers to the words that were in the \fIpwordexp\fP->\fIwe_wordv\fP list before the call, in the same order as before .LP .IP " c." 4 Pointers to the new words generated by the latest call, in the specified order .LP .RE .LP .IP " 4." 4 The count returned in \fIpwordexp\fP->\fIwe_wordc\fP shall be the total number of words from all of the calls. .LP .IP " 5." 4 The application can change any of the fields after a call to \fIwordexp\fP(), but if it does it shall reset them to the original value before a subsequent call, using the same \fIpwordexp\fP value, to \fIwordfree\fP() or \fIwordexp\fP() with the WRDE_APPEND or WRDE_REUSE flag. .LP .LP If the implementation supports the utilities defined in the Shell and Utilities volume of IEEE\ Std\ 1003.1-2001, and \fIwords\fP contains an unquoted character- , \fB'|'\fP , \fB'&'\fP , \fB';'\fP , \fB'<'\fP , \fB'>'\fP , \fB'('\fP , \fB')'\fP , \fB'{'\fP , \fB'}'\fP - in an inappropriate context, \fIwordexp\fP() shall fail, and the number of expanded words shall be 0. .LP Unless WRDE_SHOWERR is set in \fIflags\fP, \fIwordexp\fP() shall redirect \fIstderr\fP to \fB/dev/null\fP for any utilities executed as a result of command substitution while expanding \fIwords\fP. If WRDE_SHOWERR is set, \fIwordexp\fP() may write messages to \fIstderr\fP if syntax errors are detected while expanding \fIwords\fP. .LP The application shall ensure that if WRDE_DOOFFS is set, then \fIpwordexp\fP->\fIwe_offs\fP has the same value for each \fIwordexp\fP() call and \fIwordfree\fP() call using a given \fIpwordexp\fP. .LP The following constants are defined as error return values: .TP 7 WRDE_BADCHAR One of the unquoted characters- , \fB'|'\fP , \fB'&'\fP , \fB';'\fP , \fB'<'\fP , \fB'>'\fP , \fB'('\fP , \fB')'\fP , \fB'{'\fP , \fB'}'\fP - appears in \fIwords\fP in an inappropriate context. .TP 7 WRDE_BADVAL Reference to undefined shell variable when WRDE_UNDEF is set in \fIflags\fP. .TP 7 WRDE_CMDSUB Command substitution requested when WRDE_NOCMD was set in \fIflags\fP. .TP 7 WRDE_NOSPACE Attempt to allocate memory failed. .TP 7 WRDE_SYNTAX Shell syntax error, such as unbalanced parentheses or unterminated string. .sp .SH RETURN VALUE .LP Upon successful completion, \fIwordexp\fP() shall return 0. Otherwise, a non-zero value, as described in \fI\fP, shall be returned to indicate an error. If \fIwordexp\fP() returns the value WRDE_NOSPACE, then \fIpwordexp\fP->\fIwe_wordc\fP and \fIpwordexp\fP->\fIwe_wordv\fP shall be updated to reflect any words that were successfully expanded. In other cases, they shall not be modified. .LP The \fIwordfree\fP() function shall not return a value. .SH ERRORS .LP No errors are defined. .LP \fIThe following sections are informative.\fP .SH EXAMPLES .LP None. .SH APPLICATION USAGE .LP The \fIwordexp\fP() 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 \fIwordexp\fP() to process the input, the user could respond with anything that would be valid as input to the shell. .LP The WRDE_NOCMD flag is provided for applications that, for security or other reasons, want to prevent a user from executing shell commands. Disallowing unquoted shell special characters also prevents unwanted side effects, such as executing a command or writing a file. .SH RATIONALE .LP This function was included as an alternative to \fIglob\fP(). There had been continuing controversy over exactly what features should be included in \fIglob\fP(). It is hoped that by providing \fIwordexp\fP() (which provides all of the shell word expansions, but which may be slow to execute) and \fIglob\fP() (which is faster, but which only performs pathname expansion, without tilde or parameter expansion) this will satisfy the majority of applications. .LP While \fIwordexp\fP() could be implemented entirely as a library routine, it is expected that most implementations run a shell in a subprocess to do the expansion. .LP Two different approaches have been proposed for how the required information might be presented to the shell and the results returned. They are presented here as examples. .LP One proposal is to extend the \fIecho\fP utility by adding a \fB-q\fP option. This option would cause \fIecho\fP to add a backslash before each backslash and that occurs within an argument. The \fIwordexp\fP() function could then invoke the shell as follows: .sp .RS .nf \fB(void) strcpy(buffer, "echo -q"); (void) strcat(buffer,\fP \fIwords\fP\fB); if ((flags & WRDE_SHOWERR) == 0) (void) strcat(buffer, "2>/dev/null"); f = popen(buffer, "r"); \fP .fi .RE .LP The \fIwordexp\fP() function would read the resulting output, remove unquoted backslashes, and break into words at unquoted s. If the WRDE_NOCMD flag was set, \fIwordexp\fP() would have to scan \fIwords\fP before starting the subshell to make sure that there would be no command substitution. In any case, it would have to scan \fIwords\fP for unquoted special characters. .LP Another proposal is to add the following options to \fIsh\fP: .TP 7 \fB-w\fP\ \fIwordlist\fP .sp This option provides a wordlist expansion service to applications. The words in \fIwordlist\fP shall be expanded and the following written to standard output: .RS .IP " 1." 4 The count of the number of words after expansion, in decimal, followed by a null byte .LP .IP " 2." 4 The number of bytes needed to represent the expanded words (not including null separators), in decimal, followed by a null byte .LP .IP " 3." 4 The expanded words, each terminated by a null byte .LP .RE .LP If an error is encountered during word expansion, \fIsh\fP exits with a non-zero status after writing the former to report any words successfully expanded .TP 7 \fB-P\fP Run in "protected" mode. If specified with the \fB-w\fP option, no command substitution shall be performed. .sp .LP With these options, \fIwordexp\fP() could be implemented fairly simply by creating a subprocess using \fIfork\fP() and executing \fIsh\fP using the line: .sp .RS .nf \fBexecl(<\fP\fIshell path\fP\fB>, "sh", "-P", "-w",\fP \fIwords\fP\fB, (char *)0); \fP .fi .RE .LP after directing standard error to \fB/dev/null\fP. .LP It seemed objectionable for a library routine to write messages to standard error, unless explicitly requested, so \fIwordexp\fP() is required to redirect standard error to \fB/dev/null\fP to ensure that no messages are generated, even for commands executed for command substitution. The WRDE_SHOWERR flag can be specified to request that error messages be written. .LP The WRDE_REUSE flag allows the implementation to avoid the expense of freeing and reallocating memory, if that is possible. A minimal implementation can call \fIwordfree\fP() when WRDE_REUSE is set. .SH FUTURE DIRECTIONS .LP None. .SH SEE ALSO .LP \fIfnmatch\fP() , \fIglob\fP() , the Base Definitions volume of IEEE\ Std\ 1003.1-2001, \fI\fP, the Shell and Utilities volume of IEEE\ Std\ 1003.1-2001, Chapter 2, Shell Command Language .SH COPYRIGHT Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .