Knowledge learned from 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. color the output

In most cases, you want to output results with colors. For example, Green indicates success, red indicates failure, and yellow indicates warning.

Shell code

 
 

  
  
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.

2. Output debugging information

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

Shell code

 
 

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

Some geeks also provide online debugging:

Shell code

 
 

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

3. check whether a specific executable file exists?

Shell code

 
 

  
  
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, which means there is nothing to print on the control panel ).

Some geeks suggest returning Code directly by returning which.