add shellout helper

1 files changed, 54 insertions, 0 deletions

diff --git a/fuzzycat/utils.py b/fuzzycat/utils.py
index 55729a1..b43cbcf 100644
--- a/fuzzycat/utils.py
+++ b/fuzzycat/utils.py
@@ -5,6 +5,8 @@ import os
 import random
 import re
 import string
+import subprocess
+import tempfile
 
 import requests
 from glom import PathAccessError, glom
@@ -200,3 +202,55 @@ def zstdlines(filename):
                         line = prev_line + line
                     yield line
                 prev_line = lines[-1]
+
+
+def shellout(template,
+             preserve_whitespace=False,
+             executable='/bin/bash',
+             ignoremap=None,
+             encoding=None,
+             pipefail=True,
+             **kwargs):
+    """
+    Takes a shell command template and executes it. The template must use the
+    new (2.6+) format mini language. `kwargs` must contain any defined
+    placeholder, only `output` is optional and will be autofilled with a
+    temporary file if it used, but not specified explicitly.
+
+    If `pipefail` is `False` no subshell environment will be spawned, where a
+    failed pipe will cause an error as well. If `preserve_whitespace` is `True`,
+    no whitespace normalization is performed. A custom shell executable name can
+    be passed in `executable` and defaults to `/bin/bash`.
+
+    Raises RuntimeError on nonzero exit codes. To ignore certain errors, pass a
+    dictionary in `ignoremap`, with the error code to ignore as key and a string
+    message as value.
+
+    Simple template:
+
+        wc -l < {input} > {output}
+
+    Quoted curly braces:
+
+        ps ax|awk '{{print $1}}' > {output}
+
+    """
+    if not 'output' in kwargs:
+        kwargs.update({'output': tempfile.mkstemp(prefix='gluish-')[1]})
+    if ignoremap is None:
+        ignoremap = {}
+    if encoding:
+        command = template.decode(encoding).format(**kwargs)
+    else:
+        command = template.format(**kwargs)
+    if not preserve_whitespace:
+        command = re.sub('[ \t\n]+', ' ', command)
+    if pipefail:
+        command = '(set -o pipefail && %s)' % command
+    code = subprocess.call([command], shell=True, executable=executable)
+    if not code == 0:
+        if code not in ignoremap:
+            error = RuntimeError('%s exitcode: %s' % (command, code))
+            error.code = code
+            raise error
+    return kwargs.get('output')