How to use the command 'choose' (with examples)
The ‘choose’ command is a human-friendly and fast alternative to the ‘cut’ and (sometimes) ‘awk’ commands. It allows users to select specific items from a line of text, using various options and arguments.
Use case 1: Print the 5th item from a line (starting from 0)
Code:
choose 4
Motivation:
This use case is useful when you only need to extract a specific item from a line, without any other modifications. By providing the index of the item (starting from 0), you can quickly retrieve the desired information.
Explanation:
The ‘choose’ command is followed by the index of the item you want to print. The index starts from 0, which means the 5th item is referenced as 4.
Example output:
If the line is “apple orange banana grape”, the command ‘choose 4’ will print “grape”.
Use case 2: Print the first, 3rd, and 5th item from a line, where items are separated by ‘:’ instead of whitespace
Code:
choose --field-separator ':' 0 2 4
Motivation:
In some cases, the items in a line may be separated by a character other than whitespace. By specifying the field separator using the ‘–field-separator’ option, you can extract specific items based on the new separator.
Explanation:
The ‘choose’ command is followed by ‘–field-separator’, which is then followed by the desired separator (in this case, ‘:’). The indices of the items you want to print are specified after the separator.
Example output:
If the line is “apple:orange:banana:grape”, the command ‘choose –field-separator “:” 0 2 4’ will print “apple banana”.
Use case 3: Print everything from the 2nd to 5th item on the line, including the 5th
Code:
choose 1:4
Motivation:
There may be situations where you need to extract a range of items from a line, inclusive of the end index. This use case allows you to specify the starting and ending indices to print the desired items.
Explanation:
The ‘choose’ command is followed by the range of items you want to print, separated by a colon (’:’). In this case, the range is from the 2nd to the 5th item, inclusive.
Example output:
If the line is “apple orange banana grape cherry”, the command ‘choose 1:4’ will print “orange banana grape cherry”.
Use case 4: Print everything from the 2nd to 5th item on the line, excluding the 5th
Code:
choose --exclusive 1:4
Motivation:
Sometimes, you may want to exclude the last item from the range when extracting a subset of items from a line. This use case allows you to easily exclude the end index.
Explanation:
The ‘choose’ command is followed by the ‘–exclusive’ option, which indicates that the end index should be excluded from the range. The range of items is specified after the option.
Example output:
If the line is “apple orange banana grape cherry”, the command ‘choose –exclusive 1:4’ will print “orange banana grape”.
Use case 5: Print the beginning of the line to the 3rd item
Code:
choose :2
Motivation:
In some scenarios, you may only need to extract the items from the beginning of the line up to a specific index. This use case allows you to do that easily.
Explanation:
The ‘choose’ command is followed by a colon (’:’), which indicates that you want to select items from the beginning of the line. The index specifies where to stop (exclusive).
Example output:
If the line is “apple orange banana grape”, the command ‘choose :2’ will print “apple orange”.
Use case 6: Print all items from the beginning of the line until the 3rd item (exclusive)
Code:
choose --exclusive :2
Motivation:
Similar to the previous use case, you may want to extract all items from the beginning of the line up to a specific index, excluding that index. This use case allows you to easily exclude the end index.
Explanation:
The ‘choose’ command is followed by the ‘–exclusive’ option, which indicates that the end index should be excluded from the selection range. The colon (’:’) indicates the beginning of the line, and the index indicates where to stop (exclusive).
Example output:
If the line is “apple orange banana grape”, the command ‘choose –exclusive :2’ will print “apple orange”.
Use case 7: Print all items from the 3rd to the end of the line
Code:
choose 2:
Motivation:
There may be instances where you need to extract all items from a specific index until the end of the line. This use case allows you to easily select everything from the desired index onwards.
Explanation:
The ‘choose’ command is followed by the index from where you want to start printing the items. The colon (’:’) indicates the range from the specified index until the end of the line.
Example output:
If the line is “apple orange banana grape”, the command ‘choose 2:’ will print “banana grape”.
Use case 8: Print the last item from a line
Code:
choose -1
Motivation:
Occasionally, you may need to extract only the last item from a line. This use case allows you to easily select the last item without knowing the exact number of items in advance.
Explanation:
The ‘choose’ command is followed by the index -1, which represents the last item in the line.
Example output:
If the line is “apple orange banana grape”, the command ‘choose -1’ will print “grape”.
Conclusion
The ‘choose’ command provides a convenient and efficient way to extract specific items from a line of text. With its various options and arguments, you can easily select and print the desired information without resorting to more complex commands like ‘cut’ or ‘awk’.
