xref: /openbmc/openbmc-test-automation/bin/python (revision 6f149c7bfeaaa1ef1a50038618fe1e624f079963) 
1#!/bin/bash
2
3# This script is a wrapper for programs that may have alternate versions
4# (e.g. python2, python3).  This wrapper allows the user to influence the
5# selection of the program version by setting the <program name>_VERSION (e.g.
6# PYTHON_VERSION, ROBOT_VERSION, etc.) environment variable.
7
8# Users would be expected to create a link with the base name of the program
9# that points to this file.
10
11# Example:
12# cd openbmc-test-automation/bin
13# ln -s select_version python
14
15# The PATH variable should contain the expanded path to
16# openbmc-test-automation/bin.
17
18# If <program name>_VERSION is blank or not set, then the program version
19# will be whatever the system default program version is.  If <program
20# name>_VERSION is set to a value, then that value will be appened to the name
21# of the program (e.g. if PYTHON_VERSION = "3", then python3 will be used.).
22# If <program name>_VERSION is set to some value that does not correspond to a
23# valid program version for the given system, this program will fail.
24
25
26# Make sure program_name is set.
27program_name="${0##*/}"
28program_uppercase_name=${program_name^^}
29
30
31function get_target_program_path {
32  local target_program_path_var="${1:-target_program_path}" ; shift
33
34  # Get the full path to the "real" program and assign it to the variable
35  # named in target_program_path_var.
36
37  # Description of argument(s):
38  # target_program_path_var         The name of the variable to receive the
39  #                                 result.
40
41  # Example result:
42
43  # /usr/bin/python3
44
45  local version_var_name
46  local alternate_program_name
47  local base_program_path
48  local base_program_name
49  local candidate
50  local candidates
51  local base_file_path
52
53  # The typical use of this program would be to create a link to it like this:
54  # ln -s select_version python
55  # That being the case, get the name of this actual program (rather than the
56  # name of the link to it).
57  base_program_path=$(readlink -f "${0}")
58  base_program_name=${base_program_path##*/}
59
60  # Compose the version_var_name value (e.g. PYTHON_VERSION).
61  version_var_name=${program_uppercase_name}_VERSION
62  # Compose the alternate_program_name (e.g. python3).
63  alternate_program_name=${program_name}${!version_var_name}
64
65  # Now use the "type" built-in to search the PATH variable for a list of
66  # target program candidates.
67  candidates=$(type -ap ${alternate_program_name})
68
69  # Example candidates:
70  # /home/robot/openbmc-test-automation/bin/python
71  # /usr/bin/python
72
73  # In this example, the first candidate is actually a link to
74  # /home/robot/openbmc-test-automation/bin/select_version.  As such it will
75  # be rejected.
76
77  for candidate in ${candidates}
78  do
79    if [ -L "${candidate}" ] ; then
80      # The candidate is a link so we need to see if it's a link to this
81      # program file.
82      base_file_path=$(readlink "${candidate}")
83      [ "${base_file_path}" == "${base_program_name}" ] && continue
84    fi
85
86    # The candidate is NOT a link so it qualifies as the desired target
87    # program path.
88    eval ${target_program_path_var}=\"\${candidate}\"
89    return
90
91  done
92
93}
94
95
96# Main
97
98  get_target_program_path target_program_path
99
100  # Compose program path var name (e.g. PYTHON_PGM_PATH).
101  pgm_path_var_name=${program_uppercase_name}_PGM_PATH
102  # Set and export pgm_path_var_name (e.g. PYTHON_PGM_PATH=/usr/bin/python3).
103  # This value can be used by child programs for debug.
104  eval export ${pgm_path_var_name}=${target_program_path}
105
106  if [ "${1}" == "--print_only" ] ; then
107    echo "${target_program_path}"
108  else
109    # Use exec in order to replace this process with the target process.
110    exec ${target_program_path} "${@}"
111  fi
112
113