Issue running find command in python with subprocess

Question

I know this question has been asked few times already, just couldn't see what's wrong with my usage.

Usage#1

proc = subprocess.Popen(['/usr/bin/find', '/path/to/dir', '-type', 'f', '-name', '"*.gradle"', '-exec', 'grep', '"KEYWORD"', '{}', '/dev/null', ';'], stdout=PIPE, stderr=PIPE)
output, error = proc.communicate()
Error: doesn't list any files.

Usage#2

proc = subprocess.Popen(['/usr/bin/find', '/path/to/dir', '-type', 'f', '-name', '"*.gradle"', '-exec', 'grep', '"KEYWORD"', '{}', '/dev/null', '\\;'], stdout=PIPE, stderr=PIPE)
output, error = proc.communicate()
Error: find: -exec: no terminating ";" or "+"

Usage#3

proc = subprocess.Popen(['/usr/bin/find', '/path/to/dir', '-type', 'f', '-name', '"*.gradle"', '-exec', 'grep', '"KEYWORD"', '{}', '/dev/null', '\;'], stdout=PIPE, stderr=PIPE)
output, error = proc.communicate()
Error: find: -exec: no terminating ";" or "+"

I could get the command working with the shell=True option. However, would like to avoid it as a best practice.

Command works fine when run from the shell.

/usr/bin/find /path/to/dir -type f -name "*.gradle" -exec grep "KEYWORD" {} /dev/null \;

Python Version : 2.7.11
OS X 10.11.3

Appreciate any pointers on how to get this working.

Better to assign your long command to first a variable and then pass it as a parameter to Popen — Chanda Korat
– Chanda Korat, Commented Feb 23, 2017 at 11:56
Why is it a 'best practice' to not use the shell keyword argument? — Vasili Syrakis
– Vasili Syrakis, Commented Feb 23, 2017 at 12:01
@ChandaKorat - Included sample command which runs fine from the shell — ragesh
– ragesh, Commented Feb 23, 2017 at 12:10

mata · Accepted Answer · 2017-02-23 12:41:31Z

4

You don't need to use shell escapes when you build a command as list to use with Popen, so in this case \; would be interpreted as a literal backslash followed by a semicolon, while find expect to see only a semicolon as single argument. Also "KEYWORD" will include the quotes and therefore not find KEYWORD without surrounding quotes. Similar for "*.gradle", that will only match for filenames enclosed in quotes.

proc = subprocess.Popen(['/usr/bin/find', '/path/to/dir', '-type', 'f',
                         '-name', '*.gradle', '-exec', 'grep', 'KEYWORD',
                         '{}', '/dev/null', ';'],
                         stdout=PIPE, stderr=PIPE)

answered Feb 23, 2017 at 12:41

mata

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3 Comments

ragesh Over a year ago

Awesome, thanks! it worked :) Quoting the KEYWORD turned out to be the problem.

mata Over a year ago

Just one hint: adding /dev/null as input file for grep seems unneccessary, it only has the effect of making grep prepend printed lines with the filename, which you can also achieve by usig the -H (--with-filename) flag.

ragesh Over a year ago

Yes, that looks neat. Thanks!

Chanda Korat · Accepted Answer · 2017-02-23 12:26:05Z

0

Try this,

cmd='/usr/bin/find /path/to/dir -type f -name "*.gradle" -exec grep "KEYWORD" {} /dev/null \;'
proc = subprocess.Popen(cmd.split(), stdout=PIPE, stderr=PIPE)
output, error = proc.communicate()

answered Feb 23, 2017 at 12:26

Chanda Korat

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