String

Strings are probably the most basic data type in all languages, yet they hold a very important value in ABS: considering that shell scripting is all about working around command outputs, we assume you will likely work a lot with them.

Strings are enclosed by double or single quotes:

"hello world"
'hello world'

You can escape quotes with a simple backslash:

"I said: \"hello world\""

or use the other quote to ease escaping:

'I said: "hello world"'

Their individual characters can be accessed with the index notation:

"hello world"[1] # e

Accessing an index that does not exist returns an empty string.

You can access the Nth last character of the string using a negative index:

"string"[-2] # "n"

You can also access a range of the string with the [start:end] notation:

"string"[0:3] // "str"

where start is the starting position in the array, and end is the ending one. If start is not specified, it is assumed to be 0, and if end is omitted it is assumed to be the last character in the string:

"string"[:3] // "str"
"string"[1:] // "tring"

If end is negative, it will be converted to length of string - (-end):

"string"[0:-1] // "strin"

To concatenate strings, "sum" them:

"hello" + " " + "world" # "hello world"

Note that strings have what we call a "zero value": a value that evaluates to false when casted to boolean:

!!"" # false

To test for the existence of substrings within strings use the in operator:

"str" in "string"   # true
"xyz" in "string"   # false

Interpolation

You can also replace parts of the string with variables declared within your program using the $ symbol:

file = "/etc/hosts"
x = "File name is: $file"
echo(x) # "File name is: /etc/hosts"

If you need $ literals in your command, you simply need to escape them with a \:

"$non_existing_var" # "" since the ABS variable 'non_existing_var' doesn't exist
"\$non_existing_var" # "$non_existing_var"

An alternative syntax (${...}) is available for special cases -- for example, when your string is embedded within another string:

word = "word"
echo("prefix$wordsuffix") # "prefix"
echo("prefix${word}suffix") # "prefixwordsuffix"

Special characters embedded in strings

Double and single quoted strings behave differently if the string contains escaped special ASCII line control characters such as LF "\n", CR "\r", and TAB "\t".

If the string is double quoted these characters will be expanded to their ASCII codes. On the other hand, if the string is single quoted, these characters will be considered as escaped literals.

This means, for example, that double quoted LFs will cause line feeds to appear in the output:

⧐  echo("a\nb\nc")
a
b
c
⧐

Conversely, single quoted LFs will appear as escaped literal strings:

⧐  echo('a\nb\nc')
a\nb\nc
⧐

And if you need to mix escaped and unescaped special characters, then you can do this with double escapes within double quoted strings:

⧐  echo("a\\nb\nc")
a\\nb
c
⧐

Unicode support

Unicode characters are supported in strings:

⧐  echo("⺐")
⺐
⧐  echo("I ❤ ABS")
I ❤ ABS

Working with special characters in string functions

Special characters also work with split() and join() and other string functions as well.

1. Double quoted expanded special characters:

⧐  s = split("a\nb\nc", "\n")
⧐  echo(s)
[a, b, c]
⧐  ss = join(s, "\n")
⧐  echo(ss)
a
b
c
⧐

2. Single quoted literal special characters:

⧐  s = split('a\nb\nc', '\n')
⧐  echo(s)
[a, b, c]
⧐  ss = join(s, '\n')
⧐  echo(ss)
a\nb\nc
⧐

3. Double quoted, double escaped special characters:

⧐  s = split("a\\nb\\nc", "\\n")
⧐  echo(s)
[a, b, c]
⧐  ss = join(s, "\\n")
⧐  echo(ss)
a\\nb\\nc
⧐

Supported functions

any(str)

Checks whether any of the characters in str are present in the string:

"string".any("abs") # true
"string".any("xyz") # false

camel()

Converts the string to camelCase:

"a short sentence".camel() # aShortSentence

ceil()

Converts a string to a number, and then rounds the number up to the closest integer.

The string must represent a number.

"10.3".ceil() # 11
"-10.3".ceil() # -10
"a".ceil() # ERROR: ceil(...) can only be called on strings which represent numbers, 'a' given

floor()

Converts a string to a number, and then rounds the number down to the closest integer.

The string must represent a number.

"10.9".floor() # 10
"-10.9".floor() # -11
"a".floor() # ERROR: floor(...) can only be called on strings which represent numbers, 'a' given

fmt()

Formats a string (sprintf convention (opens new window)):

"hello %s".fmt("world") # "hello world"

In order to print a literal %, you can simply escape it with another %%:

"30%%".fmt() # 30%
"30%% %s".fmt("higher") # 30% higher
"30%".fmt() # 30%!(NOVERB)

index(str)

Returns the first index at which str is found:

"string".index("t") # 1
"string".index("ri") # 2

int()

Converts a string to a number, and then rounds it towards zero to the closest integer. The string must represent a number.

"99.5".int() # 99
"-99.5".int() # -99
"a".int() # ERROR: int(...) can only be called on strings which represent numbers, 'a' given

is_number()

Checks whether a string can be converted to a number:

"99.5".is_number() # true
"a".is_number() # false

Use this function when "...".number() might return an error.

json()

Parses the string as JSON, returning a hash:

⧐  s = '{"a": 1, "b": "string", "c": true, "d": {"x": 10, "y": 20}}'
⧐  h = s.json()
⧐  h
{a: 1, b: string, c: true, d: {x: 10, y: 20}}
⧐  h.d
{x: 10, y: 20}

kebab()

Converts the string to kebab-case:

"a short sentence".kebab() # a-short-sentence

last_index(str)

Returns the last index at which str is found:

"string string".last_index("g") # 13
"string string".last_index("ri") # 9

len()

Returns the length of a string:

"hello world".len() # 11

lines()

Splits a string by newline:

"first\nsecond".lines() # ["first", "second"]

lower()

Lowercases the string:

"STRING".lower() # "string"

number()

Converts a string to a number, if possible:

"99.5".number() # 99.5
"a".number() # ERROR: int(...) can only be called on strings which represent numbers, 'a' given

prefix(str)

Checks whether the string starts with str:

"string".prefix("str") # true
"string".prefix("abc") # false

repeat(i)

Creates a new string by repeating the original one i times:

"string".repeat(2) # "stringstring"

replace(str1, str2 [, n])

Replaces the first n occurrences of str1 in the string with str2. If n is omitted or negative, it will replace all occurrences:

"string".replace("i", "o", -1) # "strong"
"aaaa".replace("a", "x") # "xxxx"
"aaaa".replace("a", "x", 2) # "xxaa"
"A man, a plan, a canal, Panama!".replace("a ", "ur-") # "A man, ur-plan, ur-canal, Panama!"

reverse()

Returns a new string with the order of characters/glyphs reversed from the source.

"hello world".reverse() # "dlrow olleh"
"世界".reverse() # "界世"

round(precision?)

Converts a string to a number, and then rounds the number with the given precision.

The precision argument is optional, and set to 0 by default.

The string must represent a number.

"10.3".round() # 10
"10.6".round() # 11
"10.333".round(1) # 10.3
"a".round() # ERROR: round(...) can only be called on strings which represent numbers, 'a' given

You can also replace an array of strings:

"string".replace(["i", "g"], "o") # "strono"
"A man, a plan, a canal, Panama!".replace(["a ", "l"], "ur-") # "A man, ur-pur-an, ur-canaur-, Panama!"

snake()

Converts the string to snake_case:

"a short sentence".snake() # a_short_sentence

split(separator)

Splits a string by separator, defaulting to a single space:

"1.2.3.4".split(".") # ["1", "2", "3", "4"]
"1 2 3 4".split()    # ["1", "2", "3", "4"]

str()

Identity:

"string".str() # "string"

suffix(str)

Checks whether the string ends with str:

"string".suffix("ing") # true
"string".suffix("ong") # false

title()

Titlecases the string:

"hello world".title() # "Hello World"

trim()

Removes empty spaces from the beginning and end of the string:

" string     ".trim() # "string"

trim_by(str)

Removes str from the beginning and end of the string:

"string".trim_by("g") # "strin"
"stringest".trim_by("st") # "ringe"

upper()

Uppercases the string:

"string".upper() # "STRING"