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bash internal (293)

bash

This demonstrates the use of the bg command to resume suspended jobs in the background.

bg

bash internal process management job control background jobs

bash

This command brings the background job with job ID 1 to the foreground, allowing interaction with the process.


fg 1

bash internal process management job control foreground job

bash

This demonstrates command inspection using command -V in Bash to determine the type of a command (e.g., function, alias, or built-in).


command -V cd
#=> "cd is a function/alias/whatever"

bash internal process management command inspection command type check

bash

This demonstrates error handling in Bash using traps to catch and display errors with source file and line number information.


traperr() {
  echo "ERROR: ${BASH_SOURCE[1]} at about ${BASH_LINENO[0]}"
}

set -o errtrace
trap traperr ERR

bash internal error handling traps error trap

bash

This demonstrates how to prompt the user for input, read it, and use the input in a script.


echo "What's your name?"
read name
# Note that we didn't need to declare a new variable.
echo "Hello, $name!"

bash internal data manipulations other variable features variable assignment

bash

This demonstrates the fg command, which brings the most recent background job to the foreground, allowing it to resume execution in the current shell session.

fg

bash internal process management process control job control (foreground)

bash

This demonstrates string replacement using parameter expansion in Bash.


${FOO/from/to}

bash internal data manipulations string manipulation and expansions parameter expansion string replacement

bash

This demonstrates string comparison using == and != to check if the current user is "foo" or "bar".


## equal test
if [[ "foo" == "$USER" ]]; then
    echo "user is foo"
else
    echo "user is not foo"
fi
## not equal test
if [[ "bar" != "$USER" ]]; then
    echo "user is not bar"
else
    echo "user is bar"
fi

bash internal flow control tests (conditions)string condition

bash

This demonstrates running a command in the background using the & operator.


sleep 30 &

bash internal process management background process execution

bash

This code lists the process IDs of all background jobs currently running in the shell using the jobs -p command.


jobs -p

bash internal process management job control job listing

bash

This demonstrates the usage of the printf command in Bash for formatted output, including strings, integers, floats, and writing to files.


printf "Hello %s, I'm %s" Sven Olga
#=> "Hello Sven, I'm Olga

printf "1 + 1 = %d" 2
#=> "1 + 1 = 2"

printf "This is how you print a float: %f" 2
#=> "This is how you print a float: 2.000000"

printf '%s\n' '#!/bin/bash' 'echo hello' >file
# format string is applied to each group of arguments
printf '%i+%i=%i\n' 1 2 3  4 5 9

bash internal data manipulations string manipulation and expansions formatted output

bash

This demonstrates prefix substitution using parameter expansion in Bash.


${FOO/#from/to}

bash internal data manipulations string manipulation and expansions parameter expansion string substitution

bash

This demonstrates managing background processes in Bash, including running, listing, foregrounding, pausing, resuming, and killing jobs.


sleep 30 &
# List background jobs
jobs # => [1]+  Running                 sleep 30 &
# Bring the background job to the foreground
fg
# Ctrl-C to kill the process, or Ctrl-Z to pause it
# Resume a background process after it has been paused with Ctrl-Z
bg
# Kill job number 2
kill %2
# %1, %2, etc. can be used for fg and bg as well

bash internal process management background jobs job control

bash

This code checks the type of a specified command using the type command, ensuring the command is provided as an argument.


COMMAND=${1:?'is required'}
type $COMMAND

bash internal process management bash as a command command type checking

bash

This demonstrates a C-style for loop to iterate over a range of numbers.


for ((i = 0 ; i < 10 ; i++)); do
  echo "$i"
done

bash internal loops for loop C-style

bash

This demonstrates using the grep command to filter the output of ls -l to show only .txt files.


ls -l | grep "\.txt"

bash internal file and stream operations stream redirection and piping piping

bash

This demonstrates various uses of the cd command in Bash for directory navigation, including moving to the home directory, going up one level, navigating to a specific directory, and returning to the last directory.


cd ~    # change to home directory
cd      # also goes to home directory
cd ..   # go up one directory
        # (^^say, from /home/username/Downloads to /home/username)
cd /home/username/Documents   # change to specified directory
cd ~/Documents/..    # now in home directory (if ~/Documents exists)
cd -    # change to last directory
# => /home/username/Documents

bash internal file and stream operations directory operations directory navigation

bash

This demonstrates changing the current directory to the user's home directory.


cd ~

bash internal file and stream operations directory operations directory navigation

bash

This demonstrates a basic for loop in Bash, iterating over a list of items and printing each one.


for item in a b c; do echo "$item"; done

bash internal loops for loop basic

bash

This demonstrates capturing the output of a Bash function into a variable.


result=$(myfunc)

bash internal data manipulations string manipulation and expansions command substitution

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bash

This demonstrates the use of the bg command to resume suspended jobs in the background.

bg

bash internal process management job control background jobs

bash

This command brings the background job with job ID 1 to the foreground, allowing interaction with the process.


fg 1

bash internal process management job control foreground job

bash

This demonstrates command inspection using command -V in Bash to determine the type of a command (e.g., function, alias, or built-in).


command -V cd
#=> "cd is a function/alias/whatever"

bash internal process management command inspection command type check

bash

This demonstrates error handling in Bash using traps to catch and display errors with source file and line number information.


traperr() {
  echo "ERROR: ${BASH_SOURCE[1]} at about ${BASH_LINENO[0]}"
}

set -o errtrace
trap traperr ERR

bash internal error handling traps error trap

bash

This demonstrates how to prompt the user for input, read it, and use the input in a script.


echo "What's your name?"
read name
# Note that we didn't need to declare a new variable.
echo "Hello, $name!"

bash internal data manipulations other variable features variable assignment

bash

This demonstrates the fg command, which brings the most recent background job to the foreground, allowing it to resume execution in the current shell session.

fg

bash internal process management process control job control (foreground)

bash

This demonstrates string replacement using parameter expansion in Bash.


${FOO/from/to}

bash internal data manipulations string manipulation and expansions parameter expansion string replacement

bash

This demonstrates string comparison using == and != to check if the current user is "foo" or "bar".


## equal test
if [[ "foo" == "$USER" ]]; then
    echo "user is foo"
else
    echo "user is not foo"
fi
## not equal test
if [[ "bar" != "$USER" ]]; then
    echo "user is not bar"
else
    echo "user is bar"
fi

bash internal flow control tests (conditions)string condition

bash

This demonstrates running a command in the background using the & operator.


sleep 30 &

bash internal process management background process execution

bash

This code lists the process IDs of all background jobs currently running in the shell using the jobs -p command.


jobs -p

bash internal process management job control job listing

bash

This demonstrates the usage of the printf command in Bash for formatted output, including strings, integers, floats, and writing to files.


printf "Hello %s, I'm %s" Sven Olga
#=> "Hello Sven, I'm Olga

printf "1 + 1 = %d" 2
#=> "1 + 1 = 2"

printf "This is how you print a float: %f" 2
#=> "This is how you print a float: 2.000000"

printf '%s\n' '#!/bin/bash' 'echo hello' >file
# format string is applied to each group of arguments
printf '%i+%i=%i\n' 1 2 3  4 5 9

bash internal data manipulations string manipulation and expansions formatted output

bash

This demonstrates prefix substitution using parameter expansion in Bash.


${FOO/#from/to}

bash internal data manipulations string manipulation and expansions parameter expansion string substitution

bash

This demonstrates managing background processes in Bash, including running, listing, foregrounding, pausing, resuming, and killing jobs.


sleep 30 &
# List background jobs
jobs # => [1]+  Running                 sleep 30 &
# Bring the background job to the foreground
fg
# Ctrl-C to kill the process, or Ctrl-Z to pause it
# Resume a background process after it has been paused with Ctrl-Z
bg
# Kill job number 2
kill %2
# %1, %2, etc. can be used for fg and bg as well

bash internal process management background jobs job control

bash

This code checks the type of a specified command using the type command, ensuring the command is provided as an argument.


COMMAND=${1:?'is required'}
type $COMMAND

bash internal process management bash as a command command type checking

bash

This demonstrates a C-style for loop to iterate over a range of numbers.


for ((i = 0 ; i < 10 ; i++)); do
  echo "$i"
done

bash internal loops for loop C-style

bash

This demonstrates using the grep command to filter the output of ls -l to show only .txt files.


ls -l | grep "\.txt"

bash internal file and stream operations stream redirection and piping piping

bash


cd ~    # change to home directory
cd      # also goes to home directory
cd ..   # go up one directory
        # (^^say, from /home/username/Downloads to /home/username)
cd /home/username/Documents   # change to specified directory
cd ~/Documents/..    # now in home directory (if ~/Documents exists)
cd -    # change to last directory
# => /home/username/Documents

bash internal file and stream operations directory operations directory navigation

bash

This demonstrates changing the current directory to the user's home directory.


cd ~

bash internal file and stream operations directory operations directory navigation

bash

This demonstrates a basic for loop in Bash, iterating over a list of items and printing each one.


for item in a b c; do echo "$item"; done

bash internal loops for loop basic

bash

This demonstrates capturing the output of a Bash function into a variable.


result=$(myfunc)

bash internal data manipulations string manipulation and expansions command substitution

Previous 1

...

3 4 5

...

15 Next