expn(1) [mojave man page]
EXPN(1) General Commands Manual EXPN(1) NAME
expn - recursively expand mail aliases SYNOPSIS
expn [-a] [-v] [-w] [-d] [-1] user[@hostname] [user[@hostname]]... DESCRIPTION
expn will use the SMTP expn and vrfy commands to expand mail aliases. It will first look up the addresses you provide on the command line. If those expand into addresses on other systems, it will connect to the other systems and expand again. It will keep doing this until no further expansion is possible. OPTIONS
The default output of expn can contain many lines which are not valid email addresses. With the -aa flag, only expansions that result in legal addresses are used. Since many mailing lists have an illegal address or two, the single -a, address, flag specifies that a few ille- gal addresses can be mixed into the results. More -a flags vary the ratio. Read the source to track down the formula. With the -a option, you should be able to construct a new mailing list out of an existing one. If you wish to limit the number of levels deep that expn will recurse as it traces addresses, use the -1 option. For each -1 another level will be traversed. So, -111 will traverse no more than three levels deep. The normal mode of operation for expn is to do all of its work silently. The following options make it more verbose. It is not necessary to make it verbose to see what it is doing because as it works, it changes its argv[0] variable to reflect its current activity. To see how it is expanding things, the -v, verbose, flag will cause expn to show each address before and after translation as it works. The -w, watch, flag will cause expn to show you its conversations with the mail daemons. Finally, the -d, debug, flag will expose many of the inner workings so that it is possible to eliminate bugs. ENVIRONMENT
No environment variables are used. FILES
/tmp/expn$$ temporary file used as input to nslookup. SEE ALSO
aliases(5), sendmail(8), nslookup(8), RFC 823, and RFC 1123. BUGS
Not all mail daemons will implement expn or vrfy. It is not possible to verify addresses that are served by such daemons. When attempting to connect to a system to verify an address, expn only tries one IP address. Most mail daemons will try harder. It is assumed that you are running domain names and that the nslookup(8) program is available. If not, expn will not be able to verify many addresses. It will also pause for a long time unless you change the code where it says $have_nslookup = 1 to read $have_nslookup = 0. Lastly, expn does not handle every valid address. If you have an example, please submit a bug report. CREDITS
In 1986 or so, Jon Broome wrote a program of the same name that did about the same thing. It has since suffered bit rot and Jon Broome has dropped off the face of the earth! (Jon, if you are out there, drop me a line) AVAILABILITY
The latest version of expn is available through anonymous ftp at ftp://ftp.idiom.com/pub/muir-programs/expn. AUTHOR
David Muir Sharnoff <muir@idiom.com> 7th Edition March 11, 1993 EXPN(1)
Check Out this Related Man Page
ef_expand_file(3TECLA) Interactive Command-line Input Library Functions ef_expand_file(3TECLA) NAME
ef_expand_file, del_ExpandFile, ef_last_error, ef_list_expansions, new_ExpandFile - expand filename and wildcard expressions SYNOPSIS
cc [ flag... ] file... -ltecla [ library... ] #include <libtecla.h> ExpandFile *ef_expand_file(void); ExpandFile *del_ExpandFile(ExpandFile *ef); FileExpansion *ef_last_error(ExpandFile *ef, const char *path, int pathlen); int ef_list_expansions(FileExpansion *result, FILE *fp, int term_width); const char *new_ExpandFile(ExpandFile *ef); DESCRIPTION
The ef_expand_file() function is part of the libtecla(3LIB) library. It expands a specified filename, converting ~user/ and ~/ expressions at the start of the filename to the corresponding home directories, replacing $envvar with the value of the corresponding environment vari- able, and then, if there are any wildcards, matching these against existing filenames. Backslashes in the input filename are interpreted as escaping any special meanings of the characters that follow them. Only backslashes that are themselves preceded by backslashes are pre- served in the expanded filename. In the presence of wildcards, the returned list of filenames includes only the names of existing files which match the wildcards. Other- wise, the original filename is returned after expansion of tilde and dollar expressions, and the result is not checked against existing files. This mimics the file-globbing behavior of the UNIX tcsh shell. The supported wildcards and their meanings are: * Match any sequence of zero or more characters. ? Match any single character. [chars] Match any single character that appears in chars. If chars contains an expression of the form a-b, then any character between a and b, including a and b, matches. The '-' character loses its special meaning as a range specifier when it appears at the start of the sequence of characters. The ']' character also looses its significance as the terminator of the range expression if it appears immediately after the opening '[', at which point it is treated one of the characters of the range. If you want both '-' and ']' to be part of the range, the '-' should come first and the ']' second. [^chars] The same as [chars] except that it matches any single character that does not appear in chars. Note that wildcards never match the initial dot in filenames that start with '.'. The initial '.' must be explicitly specified in the file- name. This again mimics the globbing behavior of most UNIX shells, and its rational is based in the fact that in UNIX, files with names that start with '.' are usually hidden configuration files, which are not listed by default by the ls(1) command. The new_ExpandFile() function creates the resources used by the ef_expand_file() function. In particular, it maintains the memory that is used to record the array of matching file names that is returned by ef_expand_file(). This array is expanded as needed, so there is no builtin limit to the number of files that can be matched. The del_ExpandFile() function deletes the resources that were returned by a previous call to new_ExpandFile(). It always returns NULL (that is, a deleted object). It does nothing if the ef argument is NULL. The ef_expand_file() function performs filename expansion. Its first argument is a resource object returned by new_ExpandFile(). A pointer to the start of the filename to be matched is passed by the path argument. This must be a normal null-terminated string, but unless a length of -1 is passed in pathlen, only the first pathlen characters will be used in the filename expansion. If the length is specified as -1, the whole of the string will be expanded. A container of the following type is returned by ef_expand_file(). typedef struct { int exists; /* True if the files in files[] exist */ int nfile; /* The number of files in files[] */ char **files; /* An array of 'nfile' filenames. */ } FileExpansion; The ef_expand_file() function returns a pointer to a container whose contents are the results of the expansion. If there were no wildcards in the filename, the nfile member will be 1, and the exists member should be queried if it is important to know if the expanded file cur- rently exists. If there were wild cards, then the contained files[] array will contain the names of the nfile existing files that matched the wild-carded filename, and the exists member will have the value 1. Note that the returned container belongs to the specified ef object, and its contents will change on each call, so if you need to retain the results of more than one call to ef_expand_file(), you should either make a private copy of the returned results, or create multiple file-expansion resource objects with multiple calls to new_Expand- File(). On error, NULL is returned, and an explanation of the error can be determined by calling ef_last_error(ef). The ef_last_error() function returns the message which describes the error that occurred on the last call to ef_expand_file(), for the given (ExpandFile *ef) resource object. The ef_list_expansions() function provides a convenient way to list the filename expansions returned by ef_expand_file(). Like the ls util- ity, it arranges the filenames into equal width columns, each column having the width of the largest file. The number of columns used is thus determined by the length of the longest filename, and the specified terminal width. Beware that filenames that are longer than the specified terminal width are printed without being truncated, so output longer than the specified terminal width can occur. The list is written to the stdio stream specified by the fp argument. Thread Safety It is safe to use the facilities of this module in multiple threads, provided that each thread uses a separately allocated ExpandFile object. In other words, if two threads want to do file expansion, they should each call new_ExpandFile() to allocate their own file-expan- sion objects. EXAMPLES
Example 1 Use of file expansion function. The following is a complete example of how to use the file expansion function. #include <stdio.h> #include <libtecla.h> int main(int argc, char *argv[]) { ExpandFile *ef; /* The expansion resource object */ char *filename; /* The filename being expanded */ FileExpansion *expn; /* The results of the expansion */ int i; ef = new_ExpandFile(); if(!ef) return 1; for(arg = *(argv++); arg; arg = *(argv++)) { if((expn = ef_expand_file(ef, arg, -1)) == NULL) { fprintf(stderr, "Error expanding %s (%s). ", arg, ef_last_error(ef)); } else { printf("%s matches the following files: ", arg); for(i=0; i<expn->nfile; i++) printf(" %s ", expn->files[i]); } } ef = del_ExpandFile(ef); return 0; } ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Evolving | +-----------------------------+-----------------------------+ |MT-Level |MT-Safe | +-----------------------------+-----------------------------+ SEE ALSO
cpl_complete_word(3TECLA), gl_get_line(3TECLA), libtecla(3LIB), pca_lookup_file(3TECLA), attributes(5) SunOS 5.11 1 Jun 2004 ef_expand_file(3TECLA)