warnx(3) - f39

1err(3)                     Library Functions Manual                     err(3)
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NAME

6       err,  verr,  errx,  verrx, warn, vwarn, warnx, vwarnx - formatted error
7       messages
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LIBRARY

10       Standard C library (libc, -lc)
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SYNOPSIS

13       #include <err.h>
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15       [[noreturn]] void err(int eval, const char *fmt, ...);
16       [[noreturn]] void errx(int eval, const char *fmt, ...);
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18       void warn(const char *fmt, ...);
19       void warnx(const char *fmt, ...);
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21       #include <stdarg.h>
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23       [[noreturn]] void verr(int eval, const char *fmt, va_list args);
24       [[noreturn]] void verrx(int eval, const char *fmt, va_list args);
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26       void vwarn(const char *fmt, va_list args);
27       void vwarnx(const char *fmt, va_list args);
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DESCRIPTION

30       The err() and warn() family of functions display a formatted error mes‐
31       sage on the standard error output.  In all cases, the last component of
32       the program name, a colon character, and a space are  output.   If  the
33       fmt argument is not NULL, the printf(3)-like formatted error message is
34       output.  The output is terminated by a newline character.
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36       The err(), verr(), warn(), and vwarn() functions append an  error  mes‐
37       sage obtained from strerror(3) based on the global variable errno, pre‐
38       ceded by another colon and space unless the fmt argument is NULL.
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40       The errx() and warnx() functions do not append an error message.
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42       The err(), verr(), errx(), and verrx() functions  do  not  return,  but
43       exit with the value of the argument eval.
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ATTRIBUTES

46       For  an  explanation  of  the  terms  used  in  this  section,  see at‐
47       tributes(7).
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49       ┌─────────────────────────────────────┬───────────────┬────────────────┐
50       │Interface                            │ Attribute     │ Value          │
51       ├─────────────────────────────────────┼───────────────┼────────────────┤
52       │err(), errx(), warn(), warnx(),      │ Thread safety │ MT-Safe locale │
53       │verr(), verrx(), vwarn(), vwarnx()   │               │                │
54       └─────────────────────────────────────┴───────────────┴────────────────┘
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STANDARDS

57       BSD.
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HISTORY

60       err()
61       warn() 4.4BSD.
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EXAMPLES

64       Display the current errno information string and exit:
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66           p = malloc(size);
67           if (p == NULL)
68               err(EXIT_FAILURE, NULL);
69           fd = open(file_name, O_RDONLY, 0);
70           if (fd == -1)
71               err(EXIT_FAILURE, "%s", file_name);
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73       Display an error message and exit:
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75           if (tm.tm_hour < START_TIME)
76               errx(EXIT_FAILURE, "too early, wait until %s",
77                       start_time_string);
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79       Warn of an error:
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81           fd = open(raw_device, O_RDONLY, 0);
82           if (fd == -1)
83               warnx("%s: %s: trying the block device",
84                       raw_device, strerror(errno));
85           fd = open(block_device, O_RDONLY, 0);
86           if (fd == -1)
87               err(EXIT_FAILURE, "%s", block_device);
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