Shell-shell example

From: http://www.csdn.net/article/2013-08-15/2816581-What-I-learned-from-other-s-shell-scripts

The author Fizer Khan is a shell script fan who is so obsessed with novel and interesting things about shell scripts. He recently encountered an authy-ssh script. He learned a lot of useful and cool things to alleviate the problem of dual authentication on the SSH server. He wants to share this with you.

1. colors your echo

In most cases, you want to output echo color. For example, Green indicates success, red indicates failure, and yellow indicates warning.

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NORMAL=$(tput sgr0) GREEN=$(tput setaf 2; tput bold) YELLOW=$(tput setaf 3) RED=$(tput setaf 1)   function red() {     echo -e "$RED$*$NORMAL"}   function green() {     echo -e "$GREEN$*$NORMAL"}   function yellow() {     echo -e "$YELLOW$*$NORMAL"}  # To print success green "Task has been completed"  # To print error red "The configuration file does not exist"  # To print warning yellow "You have to use higher version."

Here, tput is used to set the color and text and reset to the normal color. For more information about tput, see prompt-color-using-tput.

II. To print debug information (print debugging information)

To print debugging information, you only need to debug and set the flag.

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function debug() {     if [[ $DEBUG ]]     then         echo ">>> $*"    fi }  # For any debug message debug "Trying to find config file"

Some geeks also provide online debugging:

123	# From cool geeks at hacker news function debug() { ((DEBUG)) && echo ">>> $*"; } function debug() { [ "$DEBUG" ] && echo ">>> $*"; }

Iii. To check specific executable exists or not (check whether a specific executable file exists)

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OK=0 FAIL=1   function require_curl() {     which curl &>/dev/null    if [ $? -eq 0 ]     then       return $OK     fi       return $FAIL }

Here we use the which command to find the executable curl path. If the execution succeeds, the executable file exists, and vice versa. Set &>/dev/null in the output stream, and the error stream will display to/dev/null (this means there is nothing to print on the control panel ).

Some geeks suggest returning Code directly by returning which.

123	# From cool geeks at hacker news function require_curl() { which "curl" &>/dev/null; } function require_curl() { which -s "curl"; }

4. To print usage of scripts (print the script used)

When I start writing shell scripts, I will use echo to print the scripts in use. When a large amount of text is in use, the echo command will become messy, so you can use Cat to set the command.

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cat << EOF   Usage: myscript <command> <arguments>   VERSION: 1.0   Available Commands       install - Install package       uninstall - Uninstall package       update - Update package       list - List packages   EOF

The

5. User configured value vs default value (User Configuration value vs default value)

Sometimes, if you do not set a value, the default value is used.

1	URL=${URL:-http://localhost:8080}

Check the URL environment variables. If it does not exist, you can specify it as localhost.

6. Check the length of the string to check the string length.

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if [ ${#authy_api_key} != 32 ] then   red "you have entered a wrong API key"  return $FAIL fi

Use $ {# variable_name} to define the length of the variable value.

VII. To read inputs with timeout (read input timeout)

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READ_TIMEOUT=60 read -t "$READ_TIMEOUT" input  # if you do not want quotes, then escape it input=$(sed "s/[;\`\"\$\' ]//g" <<< $input)  # For reading number, then you can escape other characters input=$(sed 's/[^0-9]*//g' <<< $input)

8. To get directory name and file name (get directory name and file name)

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# To find base directory APP_ROOT=`dirname "$0"`  # To find the file name filename=`basename "$filepath"`  # To find the file name without extension filename=`basename "$filepath" .html`

From: fizerkhan