String Operations

String builtins provide text manipulation, splitting, joining, and pattern matching. All return new values without modifying the original.

Case Conversion

upper

Convert a string to uppercase.

upper "hello"          # "HELLO"
"hello" | upper        # "HELLO"

lower

Convert a string to lowercase.

lower "HELLO"          # "hello"
"HELLO" | lower        # "hello"

Whitespace

trim

Remove leading and trailing whitespace.

trim "  hello  "       # "hello"
"  spaced  " | trim    # "spaced"

Splitting & Joining

split

Split a string by a delimiter, returning an array.

split "a,b,c" ","      # ["a", "b", "c"]
"one two three" | split " "   # ["one", "two", "three"]

# Split into lines
cat "log.txt" | split "\n"

# Split CSV row
"Alice,25,Engineer" | split "," 
# ["Alice", "25", "Engineer"]

join

Join an array of strings with a delimiter.

join ["a", "b", "c"] ","      # "a,b,c"
["hello", "world"] | join " " # "hello world"

# Reassemble after transformation
cat "data.csv"
  | split "\n"
  | where(fn(line) => contains line "ERROR")
  | join "\n"

Search & Match

contains

Check if a string contains a substring.

contains "hello world" "world"    # true
"hello world" | contains "xyz"    # false

# Filter lines
cat "log.txt" | split "\n" | where(fn(l) => contains l "ERROR")

starts_with

Check if a string starts with a prefix.

starts_with "hello" "hel"     # true
"README.md" | starts_with "READ"  # true

ends_with

Check if a string ends with a suffix.

ends_with "main.rs" ".rs"     # true
"photo.jpg" | ends_with ".png"    # false

Replacement

replace

Replace all occurrences of a substring.

replace "hello world" "world" "Rust"    # "hello Rust"
"foo-bar-baz" | replace "-" "_"          # "foo_bar_baz"

# Multi-step replacement
"Hello, World!"
  | replace "," ""
  | replace "!" ""
  | lower
# "hello world"

String in Pipelines

Strings integrate seamlessly with AetherShell’s pipeline model. When a single-parameter lambda receives an array, it auto-maps:

# Uppercase every element
["hello", "world"] | upper
# ["HELLO", "WORLD"]

# Trim all strings
["  a  ", " b ", "c"] | trim
# ["a", "b", "c"]

Practical Examples

Log Parsing

cat "app.log"
  | split "\n"
  | where(fn(line) => contains line "ERROR")
  | map(fn(line) => {
      let parts = split line " "
      {
        timestamp: parts[0],
        level: parts[1],
        message: join (slice parts 2 (len parts)) " "
      }
  })
  | sort_by "timestamp" "desc"
  | take 10

CSV Processing

let lines = cat "users.csv" | split "\n"
let headers = split (first lines) ","
let rows = lines | slice 1 (len lines) | map(fn(line) => split line ",")

rows | map(fn(row) => {
  name: trim row[0],
  email: lower (trim row[1]),
  dept: upper (trim row[2])
})

Text Transformation

# Snake_case to camelCase
let snake = "my_variable_name"
let parts = split snake "_"
let camel = (first parts) + (parts | slice 1 (len parts) | map(fn(p) => {
  let chars = split p ""
  (upper (first chars)) + (join (slice chars 1 (len chars)) "")
}) | join "")
echo camel   # "myVariableName"

Batch File Renaming

ls "."
  | where(fn(f) => ends_with f.name ".txt")
  | each(fn(f) => {
      let new_name = replace f.name ".txt" ".md"
      mv f.path new_name
  })

Encoding (via ab_encode / ab_decode)

For base64 and hex encoding, see the crypto builtins (crypto_base64_encode, crypto_hex_encode), or use the general ab_encode / ab_decode:

ab_encode "hello" "base64"    # "aGVsbG8="
ab_decode "aGVsbG8=" "base64" # "hello"