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bash internal (293)

Feature Group

bash internal (293)

bash

This demonstrates how to handle interruptions (Ctrl+C) gracefully in a Bash script using a trap command.


trap "echo 'Script interrupted'; exit" SIGINT
echo "Press Ctrl+C to interrupt"
sleep 10

bash internal process management signal handling trap

bash

This demonstrates accessing the process ID of the current shell session using the built-in variable $$.


echo "Current process PID: $$"

bash internal data manipulations special variables process ID variable ($$)

bash

This demonstrates setting an environment variable for a single command execution without altering the shell environment.


VAR=value  echo $VAR
#VAR=value  command_with_var

bash internal data manipulations other variable features temporary variable assignment

bash

This demonstrates declaring a read-only variable in Bash.


declare -r foo=123

bash internal data manipulations other variable features variable declaration (read-only)

bash

This code snippet measures the elapsed time of a script using Bash's built-in SECONDS variable, simulating work with sleep 2, and then calculates and displays the execution time.


start_time=$SECONDS

# Simulate some work
sleep 2

elapsed_time=$((SECONDS - start_time))
echo "Script took $elapsed_time seconds to run."

bash internal data manipulations time operations measuring elapsed time

bash

This demonstrates printing the hostname of the current system using the built-in $HOSTNAME variable.


echo "Hostname: $HOSTNAME"

bash internal environment variables built-in environment variables system information

bash

This demonstrates the use of the $$ variable to retrieve the process ID (PID) of the current shell.

$$

bash internal bash special variables process ID ($$)

bash

This demonstrates accessing and printing the current line number in a Bash script using the $LINENO variable.


echo "This is line number $LINENO"

bash internal data manipulations string manipulation and expansions special variables line number

bash

This demonstrates accessing the name of the currently executing function in Bash.


my_function() {
    echo "Current function: ${FUNCNAME[0]}"
}

my_function

bash internal code blocks function definition current function name

bash

This demonstrates exporting a variable to the environment, making it available to child processes.


export foo

bash internal process management environment variables variable export

bash

This demonstrates accessing the count of arguments passed to a Bash script.


echo "Number of arguments passed: $#"

bash internal data manipulations positional arguments argument count

bash

This demonstrates the use of the exit command to terminate a Bash script with a status code of 0, indicating successful execution.


exit 0

bash internal process management script termination exit status

bash

This demonstrates exiting a script with a status code of 1 to indicate an error or failure.


exit 1

bash internal flow control script termination exit with status code

bash

This demonstrates iterating over all arguments passed to a script using the "$@" variable.


for arg in "$@"; do
    echo "Argument: $arg"
done

bash internal loops for loop argument iteration

bash

This code checks the exit status of a failed command using $? and prints a message if the command fails.


ls /nonexistent_directory
if [ $? -ne 0 ]; then
    echo "The last command failed with exit status $?"
fi

bash internal flow control tests (conditions)exit status check

bash

This demonstrates the usage of the $0 variable to reference the current script or shell in Bash.

$0

bash internal bash special tokens $

bash

This demonstrates redirecting error output to a file using the 2> operator in Bash.


python hello.py 2> "error.err" # redirect error output to error.err

bash internal file and stream operations stream redirection and piping error output redirection

bash

This demonstrates accessing the exit status of the nth command in a pipeline using the special variable ${PIPESTATUS[n]}.


${PIPESTATUS[n]}

bash internal data manipulations other variable features exit status (PIPESTATUS)

bash

This demonstrates accessing the process ID (PID) of the current script using the built-in $$ variable.


echo "Current script PID: $$"

bash internal process management environment information process ID (PID)

bash

This demonstrates generating a random number within a specific range using the $RANDOM variable and modulo operation.


$(($RANDOM%200))  # Random number 0..199

bash internal data manipulations numeric operations random number generation

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bash

This demonstrates how to handle interruptions (Ctrl+C) gracefully in a Bash script using a trap command.


trap "echo 'Script interrupted'; exit" SIGINT
echo "Press Ctrl+C to interrupt"
sleep 10

bash internal process management signal handling trap

bash

This demonstrates accessing the process ID of the current shell session using the built-in variable $$.


echo "Current process PID: $$"

bash internal data manipulations special variables process ID variable ($$)

bash

This demonstrates setting an environment variable for a single command execution without altering the shell environment.


VAR=value  echo $VAR
#VAR=value  command_with_var

bash internal data manipulations other variable features temporary variable assignment

bash

This demonstrates declaring a read-only variable in Bash.


declare -r foo=123

bash internal data manipulations other variable features variable declaration (read-only)

bash

This code snippet measures the elapsed time of a script using Bash's built-in SECONDS variable, simulating work with sleep 2, and then calculates and displays the execution time.


start_time=$SECONDS

# Simulate some work
sleep 2

elapsed_time=$((SECONDS - start_time))
echo "Script took $elapsed_time seconds to run."

bash internal data manipulations time operations measuring elapsed time

bash

This demonstrates printing the hostname of the current system using the built-in $HOSTNAME variable.


echo "Hostname: $HOSTNAME"

bash internal environment variables built-in environment variables system information

bash

This demonstrates the use of the $$ variable to retrieve the process ID (PID) of the current shell.

$$

bash internal bash special variables process ID ($$)

bash

This demonstrates accessing and printing the current line number in a Bash script using the $LINENO variable.


echo "This is line number $LINENO"

bash internal data manipulations string manipulation and expansions special variables line number

bash

This demonstrates accessing the name of the currently executing function in Bash.


my_function() {
    echo "Current function: ${FUNCNAME[0]}"
}

my_function

bash internal code blocks function definition current function name

bash

This demonstrates exporting a variable to the environment, making it available to child processes.


export foo

bash internal process management environment variables variable export

bash

This demonstrates accessing the count of arguments passed to a Bash script.


echo "Number of arguments passed: $#"

bash internal data manipulations positional arguments argument count

bash

This demonstrates the use of the exit command to terminate a Bash script with a status code of 0, indicating successful execution.


exit 0

bash internal process management script termination exit status

bash

This demonstrates exiting a script with a status code of 1 to indicate an error or failure.


exit 1

bash internal flow control script termination exit with status code

bash

This demonstrates iterating over all arguments passed to a script using the "$@" variable.


for arg in "$@"; do
    echo "Argument: $arg"
done

bash internal loops for loop argument iteration

bash

This code checks the exit status of a failed command using $? and prints a message if the command fails.


ls /nonexistent_directory
if [ $? -ne 0 ]; then
    echo "The last command failed with exit status $?"
fi

bash internal flow control tests (conditions)exit status check

bash

This demonstrates the usage of the $0 variable to reference the current script or shell in Bash.

$0

bash internal bash special tokens $

bash

This demonstrates redirecting error output to a file using the 2> operator in Bash.


python hello.py 2> "error.err" # redirect error output to error.err

bash internal file and stream operations stream redirection and piping error output redirection

bash

This demonstrates accessing the exit status of the nth command in a pipeline using the special variable ${PIPESTATUS[n]}.


${PIPESTATUS[n]}

bash internal data manipulations other variable features exit status (PIPESTATUS)

bash

This demonstrates accessing the process ID (PID) of the current script using the built-in $$ variable.


echo "Current script PID: $$"

bash internal process management environment information process ID (PID)

bash

This demonstrates generating a random number within a specific range using the $RANDOM variable and modulo operation.


$(($RANDOM%200))  # Random number 0..199

bash internal data manipulations numeric operations random number generation

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