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path: root/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
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'


# 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