sh

sh [-aCefimnsuvx] [script [argument...]]

sh is the POSIX-compliant command interpreter (shell). It provides the standard shell scripting environment and is guaranteed to be available on all Unix-like systems.On many Linux systems, /bin/sh is a symbolic link to another shell (dash, bash, etc.) running in POSIX-compatibility mode. This provides both compatibility and performance benefits.Shell scripts beginning with #!/bin/sh use POSIX sh, ensuring maximum portability. Scripts needing bash-specific features should use #!/bin/bash instead.The shell reads commands from standard input, a file, or the -c argument. It supports variables, control flow (if, while, for, case), functions, pipelines, and I/O redirection.

-a

Export all variables that are modified or created to the environment

Prevent output redirection from overwriting existing files (noclobber)

Execute commands from string

Exit immediately if a command exits with non-zero status

Disable filename globbing (wildcard expansion)

Interactive shell

Enable job control (default for interactive shells)

Read commands but do not execute (syntax check)

Read commands from standard input

Treat unset variables as an error

Print shell input lines as they are read

Print commands and arguments as they are executed

Turn off option

~/.profile

Per-user login shell initialization file, executed for login shells.

System-wide login shell initialization file, executed before ~/.profile.

Environment variable pointing to a file executed at interactive shell startup.

Variables: NAME=value, $NAME, ${NAME}Quoting: 'literal', "interpolated", \escapeConditionals: if-then-elif-else-fi, case-esacLoops: while-do-done, for-in-do-done, until-do-doneFunctions: name() { commands; }Tests: [ condition ], test conditionArithmetic: $((expression))

POSIX sh lacks many bash features: arrays, [[ ]], brace expansion, process substitution, many string manipulations. Write portable scripts or explicitly require bash.The -e option can cause unexpected exits. Commands in conditions (if, while) or with || / && don't trigger exit on failure.Different systems link /bin/sh to different implementations (dash, bash, ksh). Test scripts on target systems or use explicit interpreters.

bash(1), dash(1), zsh(1), ksh(1), csh(1)