bash

Get execution time in seconds

 in Bash  tagged bash / GNU/Linux / howtos / modulo / random / time by

The following methods demonstrate different methods on how to compute the time a potion of code or script take to complete their execution.

[download id=”2158″]

 

Method 1 – Using date

The following example will calculate the execution time in seconds by subtracting the system date and time in seconds since 1970-01-01 00:00:00 UTC once right before the script goes to the computation part and once right after.

In order to get the system date and time in seconds since 1970-01-01 00:00:00 UTC we use the command date +%s.

[download id=”2158″]

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#!/bin/bash
 
#Print the system date and time in seconds since 1970-01-01 00:00:00 UTC
startTime=$(date +%s);
 
#We pick a random number between 1 and 10.
#Then we delay the execution for that amount of seconds.
sleep $(( (RANDOM % 10) + 1 ));
 
endTime=$(date +%s);
 
#Subtract endTime from startTime to get the total execution time
totalTime=$(($endTime-$startTime));
 
echo "Process finished after $totalTime seconds";
 
exit 0;

Method 2 – Using bash internal SECONDS variable

The following example will calculate the execution time in seconds by reseting the bash internal variable SECONDS to 0, forcing the shell to continue counting from there.

[download id=”2158″]

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#!/bin/bash
 
#This variable expands to the number of seconds since the shell was started.
#We set it to 0, forcing the shell to continue counting from there.
SECONDS=0;
 
#We pick a random number between 1 and 10.
#Then we delay the execution for that amount of seconds.
sleep $(( (RANDOM % 10) + 1 ));
 
echo "Process finished after $SECONDS seconds";
 
exit 0;

Method 3 – Using bash time

The following example uses the bash time command, which reports the time consumed by a pipeline’s execution.
When time command is executed without its complete path, then the bash built-in time command is executed, instead of the GNU time command. We will use the bash time command in this example and we will use it to run a whole block of commands.
Please note that time command will return the time in seconds as a float (i.e. there will be decimal places. e.g. 1 will be printed as 1.00).

[download id=”2158″]

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#!/bin/bash
 
#The bash time command reports the time consumed by pipeline's execution
#When time command is executed without its complete path, then the bash built-in time command is executed, instead of the GNU time command.
#We will use the bash time command in this example and we will use it to run a whole block of commands.
 
#We change the output format of time to print elapsed real time in seconds.
TIMEFORMAT="%E";
#We pick a random number between 1 and 10.
#Then we delay the execution for that amount of seconds.
totalTime=`time ( sleep $(( (RANDOM % 10) + 1 )) ) 2>&1`;
 
#Please note that time command will return the time in seconds as a float (i.e. there will be decimal places. e.g. 1 will be printed as 1.00).
#This will happen as time has build-in more precision than the first two methods presented here.
echo "Process finished after $totalTime seconds";
 
totalTimeBlock=`time (
    sleep $(( (RANDOM % 10) + 1 ));
    sleep $(( (RANDOM % 10) + 1 ));
) 2>&1`;
echo "Block finished after $totalTimeBlock seconds";
 
exit 0;

Method 4 – Using GNU time

The GNU time command runs the specified program command with the given arguments.
When time command is executed without its complete path (in our case it was /usr/bin/time), then the bash built-in time command is executed, instead of the GNU time command. To make sure we use the GNU time command, we use which to get the full path of the time command.
Please note that time command will return the time in seconds as a float (i.e. there will be decimal places. e.g. 1 will be printed as 1.00).

[download id=”2158″]

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#!/bin/bash
#The time command runs the specified program command with the given arguments.
#When time command is executed without its complete path (in our case it was /usr/bin/time), then the bash built-in time command is executed, instead of the GNU time command.
#To make sure we use the GNU time command, we use which to get the full path of the time command.
time=`which time`;
 
#We pick a random number between 1 and 10.
#Then we delay the execution for that amount of seconds.
#We change the output format of time to print elapsed real time in seconds.
totalTime="$( $time -f '%e' sleep $(( (RANDOM % 10) + 1 )) 2>&1 1>/dev/null )";
 
#Please note that time command will return the time in seconds as a float (i.e. there will be decimal places. e.g. 1 will be printed as 1.00).
#This will happen as time has build-in more precision than the first two methods presented here.
echo "Process finished after $totalTime seconds";
 
exit 0;

Notes

RANDOM internal variable

Each time RANDOM internal variable is referenced, a random integer between 0 and 32767 is generated.

By using the RANDOM variable in this command $(( (RANDOM % 10) + 1 )); we perform a modulo on the random value with the static value 10. This way we force the range of valid values to be between 0 and 9.
Later, we add 1 to that value to shift the range to be between 1 and 10.

cecho – a function to print using different colors in bash

 in Bash  tagged arguments / assosiative array / bash / color / default value / source by

The following script can be used to print colored text in bash.
You can use it in any script without copy pasting everything in it by executing the following command source cecho.sh.
Doing so, it will load to your script the functions that are defined in cecho.sh, making them available for you to use (something like including code in C, with some caveats).

[download id=”2113″]

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#!/bin/bash
 
# The following function prints a text using custom color
# -c or --color define the color for the print. See the array colors for the available options.
# -n or --noline directs the system not to print a new line after the content.
# Last argument is the message to be printed.
cecho () {
 
    declare -A colors;
    colors=(\
        ['black']='\E[0;47m'\
        ['red']='\E[0;31m'\
        ['green']='\E[0;32m'\
        ['yellow']='\E[0;33m'\
        ['blue']='\E[0;34m'\
        ['magenta']='\E[0;35m'\
        ['cyan']='\E[0;36m'\
        ['white']='\E[0;37m'\
    );
 
    local defaultMSG="No message passed.";
    local defaultColor="black";
    local defaultNewLine=true;
 
    while [[ $# -gt 1 ]];
    do
    key="$1";
 
    case $key in
        -c|--color)
            color="$2";
            shift;
        ;;
        -n|--noline)
            newLine=false;
        ;;
        *)
            # unknown option
        ;;
    esac
    shift;
    done
 
    message=${1:-$defaultMSG};   # Defaults to default message.
    color=${color:-$defaultColor};   # Defaults to default color, if not specified.
    newLine=${newLine:-$defaultNewLine};
 
    echo -en "${colors[$color]}";
    echo -en "$message";
    if [ "$newLine" = true ] ; then
        echo;
    fi
    tput sgr0; #  Reset text attributes to normal without clearing screen.
 
    return;
}
 
warning () {
 
    cecho -c 'yellow' "$@";
}
 
error () {
 
    cecho -c 'red' "$@";
}
 
information () {
 
    cecho -c 'blue' "$@";
}

 

Usage

Function cecho accepts the options to set the color and to control if a new line should be print.
Parameter -c or --color define the color for the print. See the array colors for the available options.
Parameter -n or --noline directs the system not to print a new line after the content.
The last parameter is the string message to be printed.
Functions warning, error and information are using cecho to print in color.
These three functions always print a new line and they have hardcoded one color set for each.

Example

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#Get the name of the script currently being executed
 
scriptName=$(basename $(test -L "$0" && readlink "$0" || echo "$0"));
 
#Get the directory where the script currently being executed resides
 
scriptDirDIR=$(cd $(dirname "$0") && pwd);
 
#Print in blue color with no new line
 
cecho -n -c 'blue' "$scriptDir";
 
#Print in red color with a new line following the message
 
cecho -c 'red' "$scriptName";
 
#Using the information() function to print in blue followed by a new line
 
information ‘End of script’;

Convert a list of integers from MySQL to a Bash array

 in Bash  tagged array / bash / mysql / printf by

The following code will connect to a MySQL server, it will get a list of integers and convert the results to a bash array that will be iterated using a for loop and they will be printed using zero padding.

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IDS_RAW=$(mysql --user="myuser" --password="mypass" --host="db.example.com" --database="mydb" --batch --compress --skip-column-names --execute="
  SELECT
    Id
  FROM
    Users
  WHERE
    Status = 0;
");
 
OLDIFS=$IFS;
IFS=$'\n' command eval;
'IDS=($IDS_RAW)';
IFS=$OLDIFS;
 
echo "Will process the following user IDs '${IDS[@]}'";
 
for ID in "${IDS[@]}"; do
  LEADING_ZERO=$(printf %08d $ID);
  echo "ID $LEADING_ZERO";
done;

Bash get script file name and location 1

 in Bash  tagged basename / bash / dirname / pwd / readlink / test -L by

The following code will populate the variables SCRIPT_NAME and SCRIPT_DIR with the name of the script currently being execute and the location this script is in:

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SCRIPT_NAME=$(basename $(test -L "$0" && readlink "$0" || echo "$0"));
SCRIPT_DIR=$(cd $(dirname "$0") && pwd);

Notes for SCRIPT_NAME:

  • $0 expands to the name of the shell or shell script
  • test -L "$0" checks that input is a file that exists and is a symbolic link
  • && readlink "$0" will be executed if the above statement is true and it will print the resolved symbolic link
  • || echo "$0" will be executed if the test for symbolic link fails
  • finally, basename will strip directory and suffix from whatever is returned from the above statements

Notes for SCRIPT_DIR:

  • Will not resolve the correct folder if the last component of the path is a symbolic link (symlink). It will return the location of the symlink instead of the location of the file the symlink is pointing to
  • cd will return 0 if it successfully navigates to a directory or 1 when it fails to navigate to the directory
  • cd "$( dirname "$0" )" will use dirname to strip the last component from the expanded name and try to navigate to that location
  • if the above cd fails, we get the current location using && pwd. pwd will print name of current/working directory

In case you have a problem with $0, it is overwritten or the above function is called by a child script in another folder you can replace $0 with ${BASH_SOURCE[0]}.

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SCRIPT_NAME=$(basename $(test -L "${BASH_SOURCE[0]}" && readlink "${BASH_SOURCE[0]}" || echo "${BASH_SOURCE[0]}"));
SCRIPT_DIR=$(cd $(dirname "${BASH_SOURCE[0]}") && pwd);