You can use the following basic syntax to extract the date from a string in Bash:
echo $my_string | grep -Eo '[[:digit:]]{2}/[[:digit:]]{2}/[[:digit:]]{4}'
This particular example extracts the a date in the format of mm/dd/yyyy from the string variable named my_string.
Note the following in the syntax:
- -E: The pattern should be interpreted as an extended regular expression.
- -o: Show only the part of the matching string that matches the pattern
- [:digit:]{n}: Only retrieve digits from the input with specific number
In this particular example we specified that the date had a pattern of mm/dd/yyyy in the string but you can specify another format if the date has a different format.
The following examples show how to use this syntax in several different scenarios.
Example 1: Extract Date from String with mm/dd/yyyy Format
Suppose that we have the following string:
- date_created:03/15/2024
And suppose that we would like to extract only the date from the string to get the following values:
- 03/15/2024
We can use the following syntax to do so:
my_string="date_created:03/15/2024"
echo $my_string | grep -Eo '[[:digit:]]{2}/[[:digit:]]{2}/[[:digit:]]{4}'
The following screenshot shows how to use this syntax in practice:
Notice that we’re able to extract only 03/15/2024 from the string, which represents only the date.
Example 2: Extract Date from String with yyyy-mm-dd Format
Suppose that we have the following string:
- date_created:2024-03-15:official
And suppose that we would like to extract only the date from the string to get the following values:
- 2024-03-15
We can use the following syntax to do so:
my_string="date_created:2024-03-15:official"
echo $my_string | grep -Eo '[[:digit:]]{4}-[[:digit:]]{2}-[[:digit:]]{2}'
The following screenshot shows how to use this syntax in practice:
Notice that we’re able to extract only 2024-03-15 from the string, which represents only the date.
Example 3: Extract Date from String with yyyymmdd Format
Suppose that we have the following string:
- date_created:20240315:official
And suppose that we would like to extract only the date from the string to get the following values:
- 20240315
We can use the following syntax to do so:
my_string="date_created:20240315:official"
echo $my_string | grep -Eo '[[:digit:]]{8}'
The following screenshot shows how to use this syntax in practice:
Notice that we’re able to extract only 20240315 from the string, which represents only the date.
Note that we used [[:digit:]]{8} as the pattern to look for in this example since all 8 digits in the date occurred without any separators between them.
Related Tutorials
The following tutorials explain how to perform other common tasks in Bash:
Bash: How to Extract Text Between Two Strings
Bash: How to Replace Dash with Underscore
Bash: How to Replace Multiple Characters in String
Bash: How to Replace All Occurrences of String in File
