verr(3c) - osol9

1err(3C)                  Standard C Library Functions                  err(3C)
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NAME

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

10       #include <err.h>
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12       void err(int eval, const char *fmt, ...);
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15       void verr(int eval, const char *fmt, va_list args);
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18       void errx(int eval, const char *fmt, ...);
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21       void verrx(int eval, const char *fmt, va_list args);
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24       void warn(const char *fmt, ...);
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27       void vwarn(const char *fmt, va_list args);
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30       void warnx(const char *fmt, ...);
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33       void vwarnx(const char *fmt, va_list args);
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DESCRIPTION

37       The err() and warn() family of functions display a formatted error mes‐
38       sage  on the standard error output. In all cases, the last component of
39       the program name, followed by a colon character and a space,  are  out‐
40       put.  If  the  fmt argument is not NULL, the formatted error message is
41       output. In the case of the err(), verr(),  warn(),  and  vwarn()  func‐
42       tions,  the  error  message string affiliated with the current value of
43       the global variable errno is output next, preceded by a colon character
44       and a space if fmt is not NULL. In all cases, the output is followed by
45       a newline character.  The errx(), verrx(), warnx(), and vwarnx()  func‐
46       tions will not output this error message string.
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49       The  err(),  verr(),  errx(),  and verrx() functions do not return, but
50       instead cause the program to terminate with the status value  given  by
51       the argument status.
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EXAMPLES

54       Example  1  Display  the current errno information string and terminate
55       with status indicating failure.
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57         if ((p = malloc(size)) == NULL)
58             err(EXIT_FAILURE, NULL);
59         if ((fd = open(file_name, O_RDONLY, 0)) == -1)
60             err(EXIT_FAILURE, "%s", file_name);
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63       Example 2 Display an error message and terminate with status indicating
64       failure.
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66         if (tm.tm_hour < START_TIME)
67             errx(EXIT_FAILURE, "too early, wait until %s", start_time_string);
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70       Example 3 Warn of an error.
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72         if ((fd = open(raw_device, O_RDONLY, 0)) == -1)
73             warnx("%s: %s: trying the block device",
74                 raw_device, strerror(errno));
75         if ((fd = open(block_device, O_RDONLY, 0)) == -1)
76             warn("%s", block_device);
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WARNINGS

80       It  is  important  never  to pass a string with user-supplied data as a
81       format without using `%s'. An attacker can put format specifiers in the
82       string  to  mangle the stack, leading to a possible security hole. This
83       holds true even if the string has been built ``by hand'' using a  func‐
84       tion like snprintf(3C), as the resulting string can still contain user-
85       supplied conversion specifiers for later interpolation by the err() and
86       warn() functions.
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89       Always be sure to use the proper secure idiom:
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91         err(1, "%s", string);
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ATTRIBUTES

95       See attributes(5) for descriptions of the following attributes:
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100       ┌─────────────────────────────┬─────────────────────────────┐
101       │      ATTRIBUTE TYPE         │      ATTRIBUTE VALUE        │
102       ├─────────────────────────────┼─────────────────────────────┤
103       │Interface Stability          │Committed                    │
104       ├─────────────────────────────┼─────────────────────────────┤
105       │MT-Level                     │Safe with Exceptions         │
106       └─────────────────────────────┴─────────────────────────────┘
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109       These  functions  are safe to use in multithreaded applications as long
110       as setlocale(3C) is not being called to change the locale.
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NAME

SYNOPSIS

DESCRIPTION

EXAMPLES

WARNINGS

ATTRIBUTES

SEE ALSO