Add _is_known_flag func

src/args.S

@@ -2,7 +2,7 @@
 sp_start:       .space 8
 
 .section .text
-.globl save_sp, fetch_argc, fetch_argv, has_switch
+.globl save_sp, fetch_argc, fetch_argv, has_switch, str_cmp
 
 save_sp:
     sd sp, sp_start, t0 # save the stack pointer
@@ -125,13 +125,13 @@ has_switch:
     
     mv a0, s3 # load argv buff addr into a0 (string 0)
     mv a1, s0 # move switch ptr 1 addr into a1 (string 1)
-    call _str_cmp
+    call str_cmp
     bnez a1, .LSwitchFound # if the strings match, exit loop
     beqz s1, .LSkipSecondSwitch # if we have no second switch, skip the check
 
     mv a0, s3 # move argv buff addr into a0 (string 0)
     mv a1, s1 # move switch ptr 2 addr into a1 (string 1)
-    call _str_cmp
+    call str_cmp
     bnez a1, .LSwitchFound # if the strings match, exit loop
 
     .LSkipSecondSwitch:
@@ -170,7 +170,7 @@ has_switch:
 # @param[in] a1: str buffer 2
 # @param[out] a0: result code.
 # @param[out] a1: is equal (0-no, 1-yes).
-_str_cmp:
+str_cmp:
     li t2, 0
 
     .LByteCmp:

src/main.S

@@ -35,6 +35,7 @@ flag_E:  .asciz "-E"
 .section .text
 .globl _start, show_ends
 
+# main.
 _start:
     .option push
     .option norelax
@@ -56,8 +57,15 @@ _start:
     call fetch_argv
     bnez a0, .LMainReturnErr # error if failed
     mv a0, a1
+    addi sp, sp, -8
+    sd a0, 0(sp)
+    call _is_known_flag
+    bnez a1, .LSkipArg # check if arg is flag
+    ld a0, 0(sp)
+    addi sp, sp, 8
     call cat_file
     bnez a0, .LReturnFileErr # error if failed
+    .LSkipArg:
     addi s1, s1, 1
     blt s1, s0, .LProcessFile
     j .LMainReturnOk
@@ -98,7 +106,9 @@ _start:
     ecall   # return 0
 
 
-
+# Check for flags, branch or set buffers as needed.
+# @param[in] a0: None.
+# @param[out] a0: None.
 _check_flags:
     addi sp, sp, -8
     sd ra, 0(sp)
@@ -139,3 +149,41 @@ _check_flags:
     ld ra, 0(sp)
     addi sp, sp, 8
     ret
+
+# Check if given argv is a flag to determine if cat_file should be used
+# @param[in] a0: ptr to null-terminated argv string.
+# @param[out] a0: result code.
+# @param[out] a1: found flag (0- not a flag, 1- flag).
+_is_known_flag:
+    addi sp, sp, -16
+    sd ra, 8(sp)
+    sd s0, 0(sp)
+    
+    mv s0, a0
+
+    la a0, flag_help
+    mv a1, s0
+    call str_cmp
+    bnez a1, .LFlagFound
+
+    la a0, flag_version
+    mv a1, s0
+    call str_cmp
+    bnez a1, .LFlagFound
+
+    la a0, flag_show_ends
+    mv a1, s0
+    call str_cmp
+    bnez a1, .LFlagFound
+
+    la a0, flag_E
+    mv a1, s0
+    call str_cmp
+    bnez a1, .LFlagFound
+
+    li a1, 0
+    .LFlagFound:
+    ld s0, 0(sp)
+    ld ra, 8(sp)
+    addi sp, sp, 16
+    ret