Shell Script

https://www.shellscript.sh/

Check is variable empty

if [[ -z $myvar ]]; then
    echo "myvar is empty"
else
    "myvar is $myvar"
fi

Reference:

• bash test for empty string with X“” [duplicate]

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Get current executable filename

echo "current filename is `basename $0`"

Reference:

• How do I know the script file name in a Bash script?

---

Get first file in a directory

ls *.php | head -1

Reference:

• Bash script to find the first file in a directory.

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Get modified date (in unix timestamp) of a file

echo `stat -f "%m" myfile.php`

Reference:

• me last modification date shell in script

---

Get the latest files in a directory

# Get the first file of a directory
latest_file=`ls /path/to/your/files/*.php | head -1`
# loop through all files
for f in /path/to/your/files/*.php; do
    # compare the file last modified date
    if [ `stat -f "%m" $f` -gt `stat -f "%m" $latest_file` ]; then
        latest_file=$f
    fi
done
echo "latest file $latest_file : `stat -f "%m" $latest_file`"

Reference:

• Comparing numbers in bash

---

Check is directory exists

if [ -d "$DIRECTORY" ]; then
  echo $DIRECTORY exists
fi

Or

if [ ! -d "$DIRECTORY" ]; then
  echo $DIRECTORY not exists
fi

Reference:

• How to check if a directory exists in a shell script

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Multiple condition in if statement

Example below shows to get some folders in current directory and exclude some of that

#!/bin/bash
for x in ./*; do
    if [ -d $x ]; then # Only get the directory
        proj=`basename $x`;
        if [[ $proj == "excluded_1" || $proj == "excluded_2" || $proj == "excluded_3" ]]; then
            continue
        fi
        echo $proj;
    fi
done

NOTE: for multiple conditions, must use double bracket

References:

• how to represent multiple conditions in shell script?
• How to use double or single bracket, parentheses, curly braces

---

Get current directory

currdir="`dirname $0`"

Reference:

• Can a Bash script tell what directory it’s stored in?