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python3.8
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mailcap.py
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"""Mailcap file handling. See RFC 1524.""" import os import warnings import re __all__ = ["getcaps","findmatch"] def lineno_sort_key(entry): # Sort in ascending order, with unspecified entries at the end if 'lineno' in entry: return 0, entry['lineno'] else: return 1, 0 _find_unsafe = re.compile(r'[^\xa1-\U0010FFFF\w@+=:,./-]').search class UnsafeMailcapInput(Warning): """Warning raised when refusing unsafe input""" # Part 1: top-level interface. def getcaps(): """Return a dictionary containing the mailcap database. The dictionary maps a MIME type (in all lowercase, e.g. 'text/plain') to a list of dictionaries corresponding to mailcap entries. The list collects all the entries for that MIME type from all available mailcap files. Each dictionary contains key-value pairs for that MIME type, where the viewing command is stored with the key "view". """ caps = {} lineno = 0 for mailcap in listmailcapfiles(): try: fp = open(mailcap, 'r') except OSError: continue with fp: morecaps, lineno = _readmailcapfile(fp, lineno) for key, value in morecaps.items(): if not key in caps: caps[key] = value else: caps[key] = caps[key] + value return caps def listmailcapfiles(): """Return a list of all mailcap files found on the system.""" # This is mostly a Unix thing, but we use the OS path separator anyway if 'MAILCAPS' in os.environ: pathstr = os.environ['MAILCAPS'] mailcaps = pathstr.split(os.pathsep) else: if 'HOME' in os.environ: home = os.environ['HOME'] else: # Don't bother with getpwuid() home = '.' # Last resort mailcaps = [home + '/.mailcap', '/etc/mailcap', '/usr/etc/mailcap', '/usr/local/etc/mailcap'] return mailcaps # Part 2: the parser. def readmailcapfile(fp): """Read a mailcap file and return a dictionary keyed by MIME type.""" warnings.warn('readmailcapfile is deprecated, use getcaps instead', DeprecationWarning, 2) caps, _ = _readmailcapfile(fp, None) return caps def _readmailcapfile(fp, lineno): """Read a mailcap file and return a dictionary keyed by MIME type. Each MIME type is mapped to an entry consisting of a list of dictionaries; the list will contain more than one such dictionary if a given MIME type appears more than once in the mailcap file. Each dictionary contains key-value pairs for that MIME type, where the viewing command is stored with the key "view". """ caps = {} while 1: line = fp.readline() if not line: break # Ignore comments and blank lines if line[0] == '#' or line.strip() == '': continue nextline = line # Join continuation lines while nextline[-2:] == '\\\n': nextline = fp.readline() if not nextline: nextline = '\n' line = line[:-2] + nextline # Parse the line key, fields = parseline(line) if not (key and fields): continue if lineno is not None: fields['lineno'] = lineno lineno += 1 # Normalize the key types = key.split('/') for j in range(len(types)): types[j] = types[j].strip() key = '/'.join(types).lower() # Update the database if key in caps: caps[key].append(fields) else: caps[key] = [fields] return caps, lineno def parseline(line): """Parse one entry in a mailcap file and return a dictionary. The viewing command is stored as the value with the key "view", and the rest of the fields produce key-value pairs in the dict. """ fields = [] i, n = 0, len(line) while i < n: field, i = parsefield(line, i, n) fields.append(field) i = i+1 # Skip semicolon if len(fields) < 2: return None, None key, view, rest = fields[0], fields[1], fields[2:] fields = {'view': view} for field in rest: i = field.find('=') if i < 0: fkey = field fvalue = "" else: fkey = field[:i].strip() fvalue = field[i+1:].strip() if fkey in fields: # Ignore it pass else: fields[fkey] = fvalue return key, fields def parsefield(line, i, n): """Separate one key-value pair in a mailcap entry.""" start = i while i < n: c = line[i] if c == ';': break elif c == '\\': i = i+2 else: i = i+1 return line[start:i].strip(), i # Part 3: using the database. def findmatch(caps, MIMEtype, key='view', filename="/dev/null", plist=[]): """Find a match for a mailcap entry. Return a tuple containing the command line, and the mailcap entry used; (None, None) if no match is found. This may invoke the 'test' command of several matching entries before deciding which entry to use. """ if _find_unsafe(filename): msg = "Refusing to use mailcap with filename %r. Use a safe temporary filename." % (filename,) warnings.warn(msg, UnsafeMailcapInput) return None, None entries = lookup(caps, MIMEtype, key) # XXX This code should somehow check for the needsterminal flag. for e in entries: if 'test' in e: test = subst(e['test'], filename, plist) if test is None: continue if test and os.system(test) != 0: continue command = subst(e[key], MIMEtype, filename, plist) if command is not None: return command, e return None, None def lookup(caps, MIMEtype, key=None): entries = [] if MIMEtype in caps: entries = entries + caps[MIMEtype] MIMEtypes = MIMEtype.split('/') MIMEtype = MIMEtypes[0] + '/*' if MIMEtype in caps: entries = entries + caps[MIMEtype] if key is not None: entries = [e for e in entries if key in e] entries = sorted(entries, key=lineno_sort_key) return entries def subst(field, MIMEtype, filename, plist=[]): # XXX Actually, this is Unix-specific res = '' i, n = 0, len(field) while i < n: c = field[i]; i = i+1 if c != '%': if c == '\\': c = field[i:i+1]; i = i+1 res = res + c else: c = field[i]; i = i+1 if c == '%': res = res + c elif c == 's': res = res + filename elif c == 't': if _find_unsafe(MIMEtype): msg = "Refusing to substitute MIME type %r into a shell command." % (MIMEtype,) warnings.warn(msg, UnsafeMailcapInput) return None res = res + MIMEtype elif c == '{': start = i while i < n and field[i] != '}': i = i+1 name = field[start:i] i = i+1 param = findparam(name, plist) if _find_unsafe(param): msg = "Refusing to substitute parameter %r (%s) into a shell command" % (param, name) warnings.warn(msg, UnsafeMailcapInput) return None res = res + param # XXX To do: # %n == number of parts if type is multipart/* # %F == list of alternating type and filename for parts else: res = res + '%' + c return res def findparam(name, plist): name = name.lower() + '=' n = len(name) for p in plist: if p[:n].lower() == name: return p[n:] return '' # Part 4: test program. def test(): import sys caps = getcaps() if not sys.argv[1:]: show(caps) return for i in range(1, len(sys.argv), 2): args = sys.argv[i:i+2] if len(args) < 2: print("usage: mailcap [MIMEtype file] ...") return MIMEtype = args[0] file = args[1] command, e = findmatch(caps, MIMEtype, 'view', file) if not command: print("No viewer found for", type) else: print("Executing:", command) sts = os.system(command) if sts: print("Exit status:", sts) def show(caps): print("Mailcap files:") for fn in listmailcapfiles(): print("\t" + fn) print() if not caps: caps = getcaps() print("Mailcap entries:") print() ckeys = sorted(caps) for type in ckeys: print(type) entries = caps[type] for e in entries: keys = sorted(e) for k in keys: print(" %-15s" % k, e[k]) print() if __name__ == '__main__': test()