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(4) Feature comparison

Comparison of shell features

All the shells just listed share some common features, and the major differences in syntax generally only affect script writers. It is not unusual to use one shell (e.g. tcsh) for interactive use, but another (sh or ksh) for writing scripts.

Core Similarities (and recap of basic command line usage)

Each of these items is discussed in more detail later.

Parse lines by whitespace, search for external commands using $PATH.
Can run a shell script using shellname scriptfile, or run a single command using shellname -c "command"
Pass expanded command line arguments to programs; get exit status back.
Pass environment variables to programs.
Expand filename wildcards using []*?. Each shell has some additional wildcard metacharacters, but these are common to all shells.
Standard I/O redirection and piping with <,>,>>,|
A few internal functions (cd)
Backgrounding commands with &
Quoting rules: "double quotes" protect most things, but allow $var interpretation; 'single quotes' protect all metacharacters from interpretation.
Home directory expansion using ~user (except for sh)
# comments
Command substitution using `command` (backtics)
Expand variables using $varname syntax
Conditional execution using && and ||
Line continuation with "\"

Principal Differences

between sh (+derivitives), and csh (+derivitives).

Syntax of all the flow control constructs and conditional tests.
Syntax for string manipulation inside of scripts
Syntax for arithmetic manipulation inside of scripts
Syntax for setting local variables (used only in the script) and environment variables (which are passed to child processes). setenv vs export
Syntax for redirecting I/O streams other than stdin/stdout
Login startup files (.cshrc and .login, vs .profile) and default options
Reading other shell scripts into the current shell (source filename, vs . filename)
Handling of signals (interrupts)

comparison.src last modified Mar 11, 2005

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