shell_project

This is a small shell that follows subset of POSIX shell standard.

Supported Features

• redirection operators (<, >, <<, >>)
• commandline pipe (|)
• quoting (', ")
• parameter expansion ($WORD) and environment variables management (export, env, unset)
• bulit-in commands (cd, pwd, echo, exit)
• conditional operators (&&, ||)

Prerequisite

• libreadline developer package (>= 8.12) for terminal input
• gettext for configuration

Recommend using package manager like apt or brew to install the library.

macOS

brew install readline gettext

Ubuntu

apt-get install libreadline-dev gettext

Configure and Build

Run ./configure.sh && make to configure and build.

You may need to adjust library path manually if configure script does not work.

Debug

Run make debug to build in debug mode. It will enable

• compiler options (debug symbol, sanitizer)
• parser output printing
• exit value

Test

test_script.sh receives a file that has commands to be tested. There is one test case per line. Each test case will be executed in this shell and bash. stdout, exit value pair of both will be compared to decide correctness.

Summary will be printed on stdout and details will be stored in test_log.txt.

Examples

test_case_bonus.txt

echo 'a'*
echo *$NOTHING
echo $NOTHING*
ls | cat -e && gcc -v || echo "$TERM"

stdout

#9   [OK] "echo 'a'*"
#10  [OK] "echo *$NOTHING"
#11  [OK] "echo $NOTHING*"
#12  [OK] "ls | cat -e && gcc -v || echo "$TERM""

test_log.txt

[ shell output ]
42

[ bash output ]
42

[ diff ]

shell exit status = 0
bash exit status = 0

Notes

• Syntax rules for parser is defined as form of BNF in bnf.md.
• Grammar reference
• Token recognition reference