Atlas - errno.c
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1/* SPDX-License-Identifier: GPL-3.0
2 * The Language Trail
3 *
4 * errno.c
5 *
6 * https://en.cppreference.com/w/c/header/errno.html
7 *
8 * COPYRIGHT NOTICE
9 * Copyright (C) 2025-2026 0x4248 and contributors
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the license is not changed.
12 *
13 * This software is free and open source. Licensed under the GNU general
14 * public license version 3.0 as published by the Free Software Foundation.
15*/
16
17// Here is a rundown of some error codes:
18// Note: this can differ from compiler, compiler version and system
19// 0	Success
20// 1	Operation not permitted
21// 2	No such file or directory
22// 3	No such process
23// 4	Interrupted system call
24// 5	Input/output error
25// 6	No such device or address
26// 7	Argument list too long
27// 8	Exec format error
28// 9	Bad file descriptor
29// 10	No child processes
30// 11	Resource temporarily unavailable
31// 12	Cannot allocate memory
32// 13	Permission denied
33// 14	Bad address
34// 15	Block device required
35// 16	Device or resource busy
36// 17	File exists
37// 18	Invalid cross-device link
38// 19	No such device
39// 20	Not a directory
40// 21	Is a directory
41// 22	Invalid argument
42// 23	Too many open files in system
43// 24	Too many open files
44// 25	Inappropriate ioctl for device
45// 26	Text file busy
46// 27	File too large
47// 28	No space left on device
48// 29	Illegal seek
49// 30	Read-only file system
50// 31	Too many links
51// 32	Broken pipe
52// 33	Numerical argument out of domain
53// 34	Numerical result out of range
54// 35	Resource deadlock avoided
55// 36	File name too long
56// 37	No locks available
57// 38	Function not implemented
58// 39	Directory not empty
59// 40	Too many levels of symbolic links
60// 41	Unknown error 41
61// 42	No message of desired type
62// 43	Identifier removed
63// 44	Channel number out of range
64// 45	Level 2 not synchronized
65// 46	Level 3 halted
66// 47	Level 3 reset
67// 48	Link number out of range
68// 49	Protocol driver not attached
69// 50	No CSI structure available
70// 51	Level 2 halted
71// 52	Invalid exchange
72// 53	Invalid request descriptor
73// 54	Exchange full
74// 55	No anode
75// 56	Invalid request code
76// 57	Invalid slot
77// 58	Unknown error 58
78// 59	Bad font file format
79// 60	Device not a stream
80// 61	No data available
81// 62	Timer expired
82// 63	Out of streams resources
83// 64	Machine is not on the network
84// 65	Package not installed
85// 66	Object is remote
86// 67	Link has been severed
87// 68	Advertise error
88// 69	Srmount error
89// 70	Communication error on send
90// 71	Protocol error
91// 72	Multihop attempted
92// 73	RFS specific error
93// 74	Bad message
94// 75	Value too large for defined data type
95// 76	Name not unique on network
96// 77	File descriptor in bad state
97// 78	Remote address changed
98// 79	Can not access a needed shared library
99// 80	Accessing a corrupted shared library
100// 81	.lib section in a.out corrupted
101// 82	Attempting to link in too many shared libraries
102// 83	Cannot exec a shared library directly
103// 84	Invalid or incomplete multibyte or wide character
104// 85	Interrupted system call should be restarted
105// 86	Streams pipe error
106// 87	Too many users
107// 88	Socket operation on non-socket
108// 89	Destination address required
109// 90	Message too long
110// 91	Protocol wrong type for socket
111// 92	Protocol not available
112// 93	Protocol not supported
113// 94	Socket type not supported
114// 95	Operation not supported
115// 96	Protocol family not supported
116// 97	Address family not supported by protocol
117// 98	Address already in use
118// 99	Cannot assign requested address
119// 100	Network is down
120// 101	Network is unreachable
121// 102	Network dropped connection on reset
122// 103	Software caused connection abort
123// 104	Connection reset by peer
124// 105	No buffer space available
125// 106	Transport endpoint is already connected
126// 107	Transport endpoint is not connected
127// 108	Cannot send after transport endpoint shutdown
128// 109	Too many references: cannot splice
129// 110	Connection timed out
130// 111	Connection refused
131// 112	Host is down
132// 113	No route to host
133// 114	Operation already in progress
134// 115	Operation now in progress
135// 116	Stale file handle
136// 117	Structure needs cleaning
137// 118	Not a XENIX named type file
138// 119	No XENIX semaphores available
139// 120	Is a named type file
140// 121	Remote I/O error
141// 122	Disk quota exceeded
142// 123	No medium found
143// 124	Wrong medium type
144// 125	Operation canceled
145// 126	Required key not available
146// 127	Key has expired
147// 128	Key has been revoked
148// 129	Key was rejected by service
149// 130	Owner died
150// 131	State not recoverable
151// 132	Operation not possible due to RF-kill
152// 133	Memory page has hardware error
153
154/**
155 * Errno maps these values to constants which can make it much easier to write
156 */
157
158#include <stdio.h>
159#include <errno.h>
160#include <string.h>
161
162int foo_1(){
163    return -1;
164}
165
166void foo_2(){
167    /* Rather than returning an error code we can just set errno to the error */
168    errno = ENOENT;
169}
170
171void test_notUsingErrno(){
172    int ret;
173    ret = foo_1();
174    if(ret){
175        printf("ERROR\n");
176    } else {
177        printf("OK\n");
178    }
179    return;
180}
181
182
183void test_usingErrno(){
184    foo_2();
185    /* We can read errno and then use strerror to tell the user what
186     * went wrong
187    */
188    if(errno){
189        /* ERROR: 2, No such file or directory */
190        printf("ERROR: %d, %s\n",errno, strerror(errno));
191    } else {
192        printf("OK\n");
193    }
194    return;
195}
196
197void test_stderr(){
198    /* In this demo we can het the name of an error number using stderr()
199     */
200    for (int i=0 ; i < 150; i++) {
201        printf("%d\t%s\n", i,strerror(i));
202    }
203}
204
205int main() {
206    test_notUsingErrno();
207    test_usingErrno();
208
209    return 0;
210}
211
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