referencing in cmd string

Terry Reedy tjreedy at
Sun Sep 14 17:26:11 CEST 2003

"Kali K E" <kalike2003 at> wrote in message
news:ab5a234a.0309140638.e81fbab at
> Hi,
> I wanted to grep a file for a pattern. The pattern is a dynamic one
> stored in the string "rec". I tried to do it as follows:
> cmd = "grep -c rec filelist2 > grepdata"
> os.system(cmd)

I believe you want the value of the string named 'rec', and not 'rec'
itself, inserted in your command string.  If that value does not
itself need to be quoted within the command string, then this should

"grep -c %s filelist2 > grepdata" % rec

If your pattern has chars that make it necessary to be (double?)
quoted, then maybe

'grep -c "%s" filelist2 > grepdata' % rec

will work.  (The command quoting rules depend on your OS and shell.)

Terry J. Reedy

is what you

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