cpython/Lib/commands.py

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# Module 'commands'
#
# Various tools for executing commands and looking at their output and status.
import rand
import posix
import stat
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import path
# Get 'ls -l' status for an object into a string
#
def getstatus(file):
return getoutput('ls -ld' + mkarg(file))
# Get the output from a shell command into a string.
# The exit status is ignored; a trailing newline is stripped.
# Assume the command will work with ' >tempfile 2>&1' appended.
# XXX This should use posix.popen() instead, should it exist.
#
def getoutput(cmd):
return getstatusoutput(cmd)[1]
# Ditto but preserving the exit status.
# Returns a pair (sts, output)
#
def getstatusoutput(cmd):
tmp = '/usr/tmp/wdiff' + `rand.rand()`
sts = -1
try:
sts = posix.system(cmd + ' >' + tmp + ' 2>&1')
text = readfile(tmp)
finally:
altsts = posix.system('rm -f ' + tmp)
if text[-1:] = '\n': text = text[:-1]
return sts, text
# Return a string containing a file's contents.
#
def readfile(fn):
st = posix.stat(fn)
size = st[stat.ST_SIZE]
if not size: return ''
try:
fp = open(fn, 'r')
except:
raise posix.error, 'readfile(' + fn + '): open failed'
try:
return fp.read(size)
except:
raise posix.error, 'readfile(' + fn + '): read failed'
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# Make command argument from directory and pathname (prefix space, add quotes).
#
def mk2arg(head, x):
return mkarg(path.cat(head, x))
# Make a shell command argument from a string.
# Two strategies: enclose in single quotes if it contains none;
# otherwis, enclose in double quotes and prefix quotable characters
# with backslash.
#
def mkarg(x):
if '\'' not in x:
return ' \'' + x + '\''
s = ' "'
for c in x:
if c in '\\$"':
s = s + '\\'
s = s + c
s = s + '"'
return s