My tools of the trade for python programming.
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# $Id: shell_tools.py,v 1.4 2010-01-20 21:27:41 wirawan Exp $
#
# wpylib.shell_tools
# Created: 20100106
# Wirawan Purwanto
#
# Simple and dirty tools like those I usually use in my shell
# scripts.
#
import os
import os.path
import sys
try:
import subprocess
has_subprocess = True
except:
if "has_subprocess" not in globals():
print >>sys.stderr, "Newer subprocess module does not exist, using older interfaces."
has_subprocess = False
def mcd(subdir):
# Assuming we have GNU coreutils' mkdir
mkdir("-p", subdir)
os.chdir(subdir)
def provide_file(dest, src):
"""Checks if file `dest' exists. If it does not, provide for it by means
of a softlink from `src'."""
if not os.path.exists(dest):
# strip trailing /'s just in case it exists
os.symlink(src, dest.rstrip("/"))
# Low-level utilities:
def errchk(cmd, args, retcode):
"""Checking for error after the invocation of an external command."""
if retcode == 0: return
print >>sys.stderr, "Error executing ", cmd, " ".join(args)
if retcode < 0:
err = "Command %s was terminated by signal %d" % (cmd, -retcode)
else:
err = "Command %s returned %d" % (cmd, retcode)
raise RuntimeError, err
def quote_cmdline(seq):
"""Quotes the strings in seq for feeding to shell.
This is a severe protection to prevent:
- variable, command, or other substitutions
- shell expansions (parameter, wildcard)
- word splitting
- invocation of shell builtin (!!!)
"""
# Python 2.6's subprocess.py has list2cmdline, but I don't like it because
# it still allows the shell to interpret wildcards. We have to quote wildcards
# (*, [], {}, ?) and $ as well.
rslt = []
for i in seq:
inew = '"' + i.replace("\\", "\\\\").replace('"', '\\"').replace('$', '\\$').replace('`', '\\`') + '"'
rslt.append(inew)
return " ".join(rslt)
if has_subprocess:
def run(prg, args):
retcode = subprocess.call((prg,) + tuple(args))
errchk(prg, args, retcode)
return 0
def pipe_out(args, split=False, shell=False):
"""Executes a shell command, piping out the stdout to python for parsing.
This is my customary shortcut for backtick operator.
The result is either a single string (if split==False) or a list of strings
with EOLs removed (if split==True)."""
retval = subprocess.Popen(args, stdout=subprocess.PIPE, shell=shell).communicate()[0]
if not split:
return retval
else:
return retval.splitlines()
else:
def run(prg, args=()):
# Python < 2.4 does not have subprocess, so we use spawnvp
retcode = os.spawnvp(os.P_WAIT, prg, (prg,) + tuple(args))
errchk(prg, args, retcode)
return 0
def pipe_out(args, split=False, shell=False):
"""Executes a shell command, piping out the stdout to python for parsing.
This is my customary shortcut for backtick operator.
The result is either a single string (if split==False) or a list of strings
with EOLs removed (if split==True)."""
if shell or isinstance(args, str):
# BEWARE: args should be a string in this case
p = os.popen(args, "r")
else:
args = quote_cmdline(args)
p = os.popen(args, "r")
retval = p.read()
status = p.close()
if not split:
return retval
else:
return retval.splitlines()
# coreutils
# and other common utilities
CMD = ['cat', 'cp', 'head', 'grep', 'less', 'ls', 'mkdir', 'mv', 'rm', 'tail']
CMD_NAME = {}
for n in CMD:
CMD_NAME[n] = n
s = """def %(cmd)s(*args): run(CMD_NAME['%(cmd)s'], args)"""
exec(s % {'cmd': n })
def import_commands(namespace, cmds=None):
if cmds == None: cmds = CMD
thismod = globals()
for n in cmds:
n_act = thismod[n]
namespace.setdefault(n, n_act)
"""
def cp(*args):
run('cp', args)
def mkdir(*args):
run('mkdir', args)
def mv(*args):
run('mv', args)
"""