pip install –r requirements.txt
Invalid requirement: '–r'
Traceback (most recent call last):
  File "/root/anaconda3/lib/python3.6/site-packages/pip/_vendor/packaging/requirements.py", line 93, in __init__
    req = REQUIREMENT.parseString(requirement_string)
  File "/root/anaconda3/lib/python3.6/site-packages/pip/_vendor/pyparsing.py", line 1632, in parseString
    raise exc
  File "/root/anaconda3/lib/python3.6/site-packages/pip/_vendor/pyparsing.py", line 1622, in parseString
    loc, tokens = self._parse( instring, 0 )
  File "/root/anaconda3/lib/python3.6/site-packages/pip/_vendor/pyparsing.py", line 1379, in _parseNoCache
    loc,tokens = self.parseImpl( instring, preloc, doActions )
  File "/root/anaconda3/lib/python3.6/site-packages/pip/_vendor/pyparsing.py", line 3395, in parseImpl
    loc, exprtokens = e._parse( instring, loc, doActions )
  File "/root/anaconda3/lib/python3.6/site-packages/pip/_vendor/pyparsing.py", line 1379, in _parseNoCache
    loc,tokens = self.parseImpl( instring, preloc, doActions )
  File "/root/anaconda3/lib/python3.6/site-packages/pip/_vendor/pyparsing.py", line 3717, in parseImpl
    return self.expr._parse( instring, loc, doActions, callPreParse=False )
  File "/root/anaconda3/lib/python3.6/site-packages/pip/_vendor/pyparsing.py", line 1379, in _parseNoCache
    loc,tokens = self.parseImpl( instring, preloc, doActions )
  File "/root/anaconda3/lib/python3.6/site-packages/pip/_vendor/pyparsing.py", line 3378, in parseImpl
    loc, resultlist = self.exprs[0]._parse( instring, loc, doActions, callPreParse=False )
  File "/root/anaconda3/lib/python3.6/site-packages/pip/_vendor/pyparsing.py", line 1383, in _parseNoCache
    loc,tokens = self.parseImpl( instring, preloc, doActions )
  File "/root/anaconda3/lib/python3.6/site-packages/pip/_vendor/pyparsing.py", line 2689, in parseImpl
    raise ParseException(instring, loc, self.errmsg, self)
pip._vendor.pyparsing.ParseException: Expected W:(abcd...) (at char 0), (line:1, col:1)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/root/anaconda3/lib/python3.6/site-packages/pip/_internal/req/req_install.py", line 252, in from_line
    req = Requirement(req)
  File "/root/anaconda3/lib/python3.6/site-packages/pip/_vendor/packaging/requirements.py", line 97, in __init__
    requirement_string[e.loc:e.loc + 8]))
pip._vendor.packaging.requirements.InvalidRequirement: Invalid requirement, parse error at "'–r'"