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Full Discussion: Implementing a shell in C
Top Forums Programming Implementing a shell in C Post 302096080 by jacques83 on Monday 13th of November 2006 09:09:13 PM
Old 11-13-2006
Implementing a shell in C

Hi,

I am implementing a shell in C, with the following problem...

Suppose the shell is invoked from the command line as
>> myshell < test.in > test.out 2>&1

I have to execute the commands in test.in and redirect them to test.out
How does one detect in the main function that the shell has been
invoked with input and
output redirection files? Invoking it thus, I do not get any parameters
in argv[].
Also can one detect the "2>&1" part to direct stderr to stdout?
 

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CMDTEST(1)						      General Commands Manual							CMDTEST(1)

NAME
cmdtest - blackbox testing of Unix command line tools SYNOPSIS
cmdtest [-c=COMMAND] [--command=COMMAND] [--config=FILE] [--dump-config] [--dump-memory-profile=METHOD] [--dump-setting-names] [--generate-manpage=TEMPLATE] [-h] [--help] [-k] [--keep] [--list-config-files] [--log=FILE] [--log-keep=N] [--log-level=LEVEL] [--log-max=SIZE] [--no-default-configs] [--output=FILE] [-t=TEST] [--test=TEST] [--timings] [--version] [FILE]... DESCRIPTION
cmdtest black box tests Unix command line tools. Given some test scripts, their inputs, and expected outputs, it verifies that the command line produces the expected output. If not, it reports problems, and shows the differences. Each test case foo consists of the following files: foo.script a script to run the test (this is required) foo.stdin the file fed to standard input foo.stdout the expected output to the standard output foo.stderr the expected output to the standard error foo.exit the expected exit code foo.setup a shell script to run before the test foo.teardown a shell script to run after test Usually, a single test is not enough. All tests are put into the same directory, and they may share some setup and teardown code: setup-once a shell script to run once, before any tests setup a shell script to run before each test teardown a shell script to run after each test teardown-once a shell script to run once, after all tests cmdtest is given the name of the directory with all the tests, or several such directories, and it does the following: o execute setup-once o for each test case (unique prefix foo): -- execute setup -- execute foo.setup -- execute the command, by running foo.script, and redirecting standard input to come from foo.stdin, and capturing standard output and error and exit codes -- execute foo.teardown -- execute teardown -- report result of test: does exit code match foo.exit, standard output match foo.stdout, and standard error match foo.stderr? o execute teardown-once Except for foo.script, all of these files are optional. If a setup or teardown script is missing, it is simply not executed. If one of the standard input, output, or error files is missing, it is treated as if it were empty. If the exit code file is missing, it is treated as if it specified an exit code of zero. The shell scripts may use the following environment variables: DATADIR a temporary directory where files may be created by the test TESTNAME name of the current test (will be empty for setup-once and teardown-once) SRCDIR directory from which cmdtest was launched OPTIONS
-c, --command=COMMAND ignored for backwards compatibility --config=FILE add FILE to config files --dump-config write out the entire current configuration --dump-memory-profile=METHOD make memory profiling dumps using METHOD, which is one of: none, simple, meliae, or heapy (default: simple) --dump-setting-names write out all names of settings and quit --generate-manpage=TEMPLATE fill in manual page TEMPLATE -h, --help show this help message and exit -k, --keep keep temporary data on failure --list-config-files list all possible config files --log=FILE write log entries to FILE (default is to not write log files at all); use "syslog" to log to system log --log-keep=N keep last N logs (10) --log-level=LEVEL log at LEVEL, one of debug, info, warning, error, critical, fatal (default: debug) --log-max=SIZE rotate logs larger than SIZE, zero for never (default: 0) --no-default-configs clear list of configuration files to read --output=FILE write output to FILE, instead of standard output -t, --test=TEST run only TEST (can be given many times) --timings report how long each test takes --version show program's version number and exit EXAMPLE
To test that the echo(1) command outputs the expected string, create a file called echo-tests/hello.script containing the following con- tent: #!/bin/sh echo hello, world Also create the file echo-tests/hello.stdout containing: hello, world Then you can run the tests: $ cmdtest echo-tests test 1/1 1/1 tests OK, 0 failures If you change the stdout file to be something else, cmdtest will report the differences: $ cmdtest echo-tests FAIL: hello: stdout diff: --- echo-tests/hello.stdout 2011-09-11 19:14:47 +0100 +++ echo-tests/hello.stdout-actual 2011-09-11 19:14:49 +0100 @@ -1 +1 @@ -something else +hello, world test 1/1 0/1 tests OK, 1 failures Furthermore, the echo-tests directory will contain the actual output files, and diffs from the expected files. If one of the actual output files is actually correct, you can actualy rename it to be the expected file. Actually, that's a very convenient way of creating the ex- pected output files: you run the test, fixing things, until you've manually checked the actual output is correct, then you rename the file. SEE ALSO
cliapp(5). CMDTEST(1)
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