second commit

.gitignore

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+fsh

fsh.nimble

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+# Package
+
+version       = "0.1.0"
+author        = "Sekulum Forka"
+description   = "A shell inspired by tcl"
+license       = "AGPL-3.0-only"
+srcDir        = "src"
+bin           = @["fsh"]
+
+
+# Dependencies
+
+requires "nim >= 1.4.4"

src/fsh.nim

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+# fsh - Forka shell
+# 2021 - Seculum Forka
+# This program is licensed under the agpl v3.0 only license
+
+# imports
+import streams
+import strutils
+import osproc
+
+# forward declarations
+proc eval(cmd: string): string
+
+# skipSpaces reads the stream until a non-space character is found
+proc skipSpaces(strm: Stream): int =
+  while not strm.atEnd():
+    if strm.peekChar() == ' ':
+      discard strm.readChar()
+      result.inc
+    else: break
+
+# readLiterals parses the string passed in as a literal, preserving all braces except the first and last ones
+proc readLiteral(strm: Stream): string =
+  var numbraces=1
+  while not strm.atEnd() and numbraces > 0:
+    let c = strm.readChar()
+    case c:
+      of '{':
+        numbraces.inc
+      of '}':
+        numbraces = numbraces - 1
+      of '\\':
+        if strm.peekChar notin {'{', '}'}: result.add(strm.readChar)
+        result.add(strm.readChar)
+      else:
+        result.add(c)
+
+# a forward declaration. Fuck this shit
+proc readSubstitution(strm: Stream): string
+
+# readInterpelation reads the interpelation in etween [ and  ]
+proc readInterpelation(strm: Stream): string =
+  while not strm.atEnd():
+    let c = strm.readChar()
+    case c:
+      of '{':
+        result.add('{')
+        result.add(strm.readLiteral)
+        result.add('}')
+      of '[':
+        result.add('[')
+        result.add(strm.readInterpelation)
+        result.add(']')
+      of '"':
+        result.add("\"")
+        result.add(strm.readSubstitution)
+        result.add("\"")
+      of '\\':
+        result.add("\\")
+        result.add(strm.readChar())
+      of ']':
+        break
+      else: result.add(c)
+
+# readSubstitution reads a substitutionbetween "quotes"
+proc readSubstitution(strm: Stream): string =
+  while not strm.atEnd():
+    let c = strm.readChar()
+    case c:
+      of '{':
+        result.add('{')
+        result.add(strm.readLiteral)
+        result.add('}')
+      of '[':
+        result.add('[')
+        result.add(strm.readInterpelation)
+        result.add(']')
+      of '"':
+        break
+      of '\\':
+        result.add("\\")
+        result.add(strm.readChar())
+      else: result.add(c)
+
+# readCommand reads a command from stream
+proc readCommand(strm: Stream): string =
+  while not strm.atEnd():
+    let c = strm.readChar()
+    case c:
+      of '{':
+        result.add('{')
+        result.add(strm.readLiteral)
+        result.add('}')
+      of '[':
+        result.add('[')
+        result.add(strm.readInterpelation)
+        result.add(']')
+      of '"':
+        result.add("\"")
+        result.add(strm.readSubstitution)
+        result.add("\"")
+      of '\\':
+        result.add("\\")
+        result.add(strm.readChar())
+      of '\n', '\r', ';': break
+      else: result.add(c)
+
+# substitute does a substitution on the stream passed in
+proc substitute(strm: Stream, delim=";\p"): string =
+  while not strm.atEnd():
+    let c = strm.readChar()
+    if c in delim: break
+    case c:
+      of '{':
+        result.add(strm.readLiteral)
+      of '}':
+        stderr.write("Extra closing brace")
+      of '[':
+        result.add(strm.readInterpelation.eval)
+      of ']':
+        stderr.write("Extra closing bracket")
+      of '\\':
+        result.add(strm.readChar())
+      else:
+        result.add(c)
+
+# parseCommand parses the string given into a list representing a command
+proc parseCommand(cmd: string): seq[string] =
+  var newitem = ""
+  let strm = newStringStream(cmd)
+  while true:
+    if strm.atEnd():
+      result.add(newitem)
+      break
+    let c = strm.readChar()
+    case c:
+      of '{':
+        newitem.add(strm.readLiteral)
+      of '[':
+        newitem.add(strm.readInterpelation.eval)
+      of '"':
+        newitem.add(strm.readSubstitution.newStringStream.substitute)
+      of ' ':
+        result.add(newitem)
+        newitem = ""
+        discard strm.skipSpaces()
+      else: newitem.add(c)
+
+# executes executes the command. For now it involves catting the command and printing it
+proc execute(cmd: seq[string]): string =
+  let progname=cmd[0]
+  let args = cmd[1..cmd.high]
+  let ps = startProcess(progname, args=args, options={poUsePath})
+  result=ps.outputStream.readAll
+  ps.close
+  
+
+# eval evaluates the given string
+proc eval(cmd: string): string =
+  let parsed = cmd.parseCommand
+  result = parsed.execute
+
+when isMainModule:
+  let stdinstrm = stdin.newFileStream
+  while not stdinstrm.atEnd():
+    stdinstrm.readCommand.eval.echo