src/file.S

@@ -1,5 +1,6 @@
 .data
-cat_buf:    .space 4096
+cat_buf:        .space 4096
+endings_buf:    .space 4097
 
 .section .text
 .globl cat_file, open_fd, cat_stdin
@@ -8,6 +9,11 @@ cat_buf:    .space 4096
 # @param[in] a0: ptr to null-terminated file str.
 # @param[out] a0: result code.
 cat_file:
+    addi sp, sp, -24
+    sd s0, 0(sp)
+    sd ra, 8(sp)
+    sd s1, 16(sp)
+
     mv a1, a0 # since the function takes in a0, move it to a1 for syscall
     
     addi sp, sp, -8
@@ -16,21 +22,30 @@ cat_file:
     ld ra, 0(sp)
     addi sp, sp, 8
 
-    mv t0, a1 # put fd in t0
+    mv s0, a1 # put fd in s0
+    la t1, show_ends
+    lb s1, 0(t1) # store if we show ends into s1
+
     beqz a0, .LReadFileBlock # if we don't have an error, jump to reading
     li a0, 1
     j .LCatFileRet
 
 
     .LReadFileBlock:
-    mv a0, t0
+    mv a0, s0
     la a1, cat_buf
     li a2, 4096
     li a7, 63
     ecall
     blez a0, .LCloseFD # if we haven't read any bytes, EOF, close FD
-    mv a2, a0 # move bytes read into bytes needed to write
+    beqz s1, .LNoEndingsWrite
+    mv a1, a0
+    la a0, cat_buf
+    call _stdout_add_endings
+    j .LReadFileBlock
 
+    .LNoEndingsWrite:
+    mv a2, a0 # load the amount of bytes read in previous step into bytes needed to write
     li a0, 1
     la a1, cat_buf
     li a7, 64
@@ -38,11 +53,15 @@ cat_file:
     j .LReadFileBlock
     
     .LCloseFD:
-    mv a0, t0
+    mv a0, s0
     li a7, 57 # close fd
     ecall
 
     .LCatFileRet:
+    ld s0, 0(sp)
+    ld ra, 8(sp)
+    ld s1, 16(sp)
+    addi sp, sp, 24
     ret
 
 # Cat out stdin to stdout
@@ -89,19 +108,91 @@ open_fd:
     2:
     ret
 
-# # Check if the given file exists without opening fd
-# # @param[in] a0: ptr to null-terminated file str.
-# # @param[out] a0: result code (0-exists 1-doesn't exist).
-# file_exists:
-#     mv a1, a0
-#     li a0, -100 # relative/absolute path
-#     li a2, 0
-#     li a7, 48
-#     ecall
-#     beqz a0, 1f
-#     li a0, 1
-#     ret
+# Print to stdout while adding "$" characters.
+# @param[in] a0: ptr to null-terminated str.
+# @param[in] a1: length of str.
+# @param[out] a0: result code.
+_stdout_add_endings:
+    addi sp, sp, -72
+    sd s7, 64(sp)
+    sd s6, 56(sp)
+    sd s5, 48(sp)
+    sd s4, 40(sp)
+    sd ra, 32(sp)
+    sd s3, 24(sp)
+    sd s2, 16(sp)
+    sd s1, 8(sp)
+    sd s0, 0(sp)
 
-#     1:
-#     li a0, 0
-#     ret
+
+    mv s0, a0 # put the cat_buf ptr in s0
+    mv s1, a1
+    li s2, 0 # set the cat_buf char counter to 0
+    li s3, 0 # set the endings_buf char counter to 0
+    
+    la s5, endings_buf
+    .LStdoutEndingsProcessChunk:
+    add s4, s0, s2 # Calculate the offset address
+    lb t6, 0(s4)
+    li t4, 0xA # newline
+    bne t6, t4, 1f # if the current byte is not a newline, skip to writing
+
+    add s4, s5, s3 # s4 = endings_buf[s2]
+    li t5, '$'
+    sb t5, 0(s4) # endings_buf[s2] = $
+    li t5, '\n'
+    addi s4, s4, 1
+    sb t5, 0(s4) # endings_buf[s2] = \n
+    addi s3, s3, 2
+
+    li a0, 1
+    la a1, endings_buf
+    mv a2, s3
+    li a7, 64
+    ecall
+    call _zero_endings_buf
+    li s3, 0 # reset endings_buf char counter
+    j 2f
+
+    1:
+    add s4, s5, s3 # s4 = endings_buf[s2]
+    sb t6, 0(s4) # endings_buf[s2] = t6
+
+    addi s3, s3, 1 # inc endings_buf pointer
+    2:
+    addi s2, s2, 1 # inc cat_buf pointer
+    blt s2, s1, .LStdoutEndingsProcessChunk
+    beqz s3, .LSkipEndingsPrint
+    li a0, 1
+    la a1, endings_buf
+    mv a2, s3
+    li a7, 64
+    ecall
+    .LSkipEndingsPrint:
+
+    li a0, 0
+
+    ld s0, 0(sp)
+    ld s1, 8(sp)
+    ld s2, 16(sp)
+    ld s3, 24(sp)
+    ld ra, 32(sp)
+    ld s4, 40(sp)
+    ld s5, 48(sp)
+    ld s6, 56(sp)
+    ld s7, 64(sp)
+    addi sp, sp, 72
+    ret
+
+_zero_endings_buf:
+    li t0, 0
+    li t1, 4097
+
+    .LZeroEndingsBufByte:
+    la t2, endings_buf
+    add t2, t2, t0
+    sb x0, 0(t2)
+    addi t0, t0, 1
+    blt t0, t1, .LZeroEndingsBufByte
+
+    ret

src/main.S

@@ -1,5 +1,6 @@
 .data
 argc:           .space 8
+show_ends:      .space 1
 
 cat_prefix:     .ascii "cat: "
 .equ CAT_PREFIX_LEN, . - cat_prefix
@@ -11,13 +12,14 @@ help:
     .ascii "Usage: cat [OPTION]... [FILE]...\n"
     .ascii "Concatenate FILE(S) to standard output.\n\n"
     .ascii "With no FILE, or when FILE is -, read standard input.\n\n"
-    .ascii "    --help       display this help and exit\n"
-    .ascii "    --version    output version information and exit\n\n"
+    .ascii "    -E, --show-ends     display $ at end of each line\n"
+    .ascii "    --help              display this help and exit\n"
+    .ascii "    --version           output version information and exit\n\n"
     .asciz "Git repository: <https://git.lexza.ch/Lexzach/riscv-cat>\n"
 .equ HELP_LEN, . - help
 
 version:
-    .ascii "cat 1.0.0\n"
+    .ascii "cat 1.1.0\n"
     .ascii "Copyright (C) 2026 lexzach\n"
     .ascii "License MIT\n"
     .ascii "This is free software: you are free to change and redistribute it.\n"
@@ -26,10 +28,12 @@ version:
 .equ VERSION_LEN, . - version
 
 flag_help:     .asciz "--help"
-flag_version:     .asciz "--version"
+flag_version:  .asciz "--version"
+flag_show_ends:  .asciz "--show-ends"
+flag_E:  .asciz "-E"
 
 .section .text
-.globl _start
+.globl _start, show_ends
 
 _start:
     .option push
@@ -113,7 +117,7 @@ _check_flags:
 
     .LSkipDispHelp:
     
-    la a0, flag_version # help flag
+    la a0, flag_version # version flag
     li a1, 0 # no second flag
     call has_switch
     bnez a0, .LMainReturnErr
@@ -126,6 +130,12 @@ _check_flags:
     j .LMainReturnOk
     .LSkipDispVersion:
 
+    la a0, flag_show_ends # show ends flag
+    la a1, flag_E # show ends -E flag
+    call has_switch
+    bnez a0, .LMainReturnErr
+    sb a1, show_ends, t1 # since the return for has switch is either 0 for not found or 1 for found, we can just write it directly into the buf
+    
     ld ra, 0(sp)
     addi sp, sp, 8
     ret