README.md

@@ -16,6 +16,8 @@ Run the `make` command in the root of the repository.
 
 Options:
 
+`-b, --number-nonblank` - number nonempty output lines, overrides -n
 `-E, --show-ends` - display $ at end of each line\
+`-n, --number` - number all output lines
 `--help` - Show the help page.\
 `--version` - Show the version page.

src/main.S

@@ -1,7 +1,8 @@
 .data
-argc:           .space 8
+argc:               .space 8
-show_ends:      .space 1
+show_ends:          .space 1
-number:         .space 1
+number:             .space 1
+number_nonblank:    .space 1
 
 cat_prefix:     .ascii "cat: "
 .equ CAT_PREFIX_LEN, . - cat_prefix
@@ -13,15 +14,16 @@ 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 "    -E, --show-ends     display $ at end of each line\n"
+    .ascii "    -b, --number-nonblank   number nonempty output lines, overrides -n\n"
-    .ascii "    -n, --number        number all output lines\n"
+    .ascii "    -E, --show-ends         display $ at end of each line\n"
-    .ascii "    --help              display this help and exit\n"
+    .ascii "    -n, --number            number all output lines\n"
-    .ascii "    --version           output version information and exit\n\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 1.3.0\n"
+    .ascii "cat 1.4.0\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"
@@ -35,9 +37,11 @@ flag_show_ends:  .asciz "--show-ends"
 flag_E:  .asciz "-E"
 flag_number: .asciz "--number"
 flag_n: .asciz "-n"
+flag_number_nonblank: .asciz "--number-nonblank"
+flag_b: .asciz "-b"
 
 .section .text
-.globl _start, show_ends, number
+.globl _start, show_ends, number, number_nonblank
 
 # main.
 _start:
@@ -162,6 +166,12 @@ _check_flags:
     bnez a0, .LMainReturnErr
     sb a1, number, t1
 
+    la a0, flag_number_nonblank
+    la a1, flag_b
+    call has_switch
+    bnez a0, .LMainReturnErr
+    sb a1, number_nonblank, t1
+
     ld ra, 0(sp)
     addi sp, sp, 8
     ret
@@ -207,6 +217,16 @@ _is_known_flag:
     call str_cmp
     bnez a1, .LFlagFound
 
+    la a0, flag_number_nonblank
+    mv a1, s0
+    call str_cmp
+    bnez a1, .LFlagFound
+
+    la a0, flag_b
+    mv a1, s0
+    call str_cmp
+    bnez a1, .LFlagFound
+
     li a1, 0
     .LFlagFound:
     ld s0, 0(sp)

src/mod.S

@@ -68,11 +68,11 @@ add_endings:
 # @param[in] a0: ptr to null-terminated str.
 # @param[in] a1: length of str.
 # @param[in] a2: mod buf addr.
-# @param[in] a3: skip empty.
 # @param[out] a0: result code.
 # @param[out] a1: bytes written to mod buf.
 add_line_numbers:
-    addi sp, sp, -64
+    addi sp, sp, -72
+    sd s7, 64(sp) # skip empty
     sd s6, 56(sp) # mod buf ptr
     sd s5, 48(sp) # mod buf bp
     sd s4, 40(sp) # str buf ptr
@@ -82,6 +82,8 @@ add_line_numbers:
     sd s1, 8(sp) # len of str
     sd s0, 0(sp) # str buf addr
 
+    la t0, number_nonblank
+    lb s7, 0(t0)
 
     mv s0, a0 # put the str ptr in s0
     mv s1, a1 # move length of str into s1
@@ -111,11 +113,20 @@ add_line_numbers:
     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
+    bne t6, t4, 1f # if the current byte IS NOT a newline, skip to writing
     mv t0, s2
     addi t0, t0, 1 # move ahead one char and see if EOF
-    bge t0, s1, 1f # if the newline is at the veyr end, we don't indicate a new line number
+    bge t0, s1, 1f # if the newline is at the very end, we don't indicate a new line number
+    beqz s7, .LLineNumbersSkipEmptyCheck
     
+    mv t0, s4 # move the current string buf pointer into t0
+    li t1, 1
+    sub t0, t0, t1 # move the str pointer back one
+    lb t0, 0(t0)
+    # t4 still contains a newline char
+    beq t0, t4, 1f # if the previous byte IS a newline, skip to writing
+    
+    .LLineNumbersSkipEmptyCheck:
     
     call _inc_line_count
     
@@ -165,7 +176,8 @@ add_line_numbers:
     ld s4, 40(sp)
     ld s5, 48(sp)
     ld s6, 56(sp)
-    addi sp, sp, 64
+    ld s6, 64(sp)
+    addi sp, sp, 72
     ret