---
name: "err"
section: "3"
platform: "linux"
package: "man-pages"
version: "6.19-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "freebsd", "macos"]
url: "https://new.carta.tech/err"
---

# err(3)

formatted error messages

## NAME

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

## LIBRARY

Standard C library (*libc*, *-lc*)

## SYNOPSIS

```
#include <err.h>
```

**\[\[noreturn\]\] void err(int** *eval***, const char \****fmt***, ...);** **\[\[noreturn\]\] void errx(int** *eval***, const char \****fmt***, ...);**

**void warn(const char \****fmt***, ...);** **void warnx(const char \****fmt***, ...);**

**#include \<stdarg.h\>**

**\[\[noreturn\]\] void verr(int** *eval***, const char \****fmt***, va\_list** *args***);** **\[\[noreturn\]\] void verrx(int** *eval***, const char \****fmt***, va\_list** *args***);**

**void vwarn(const char \****fmt***, va\_list** *args***);** **void vwarnx(const char \****fmt***, va\_list** *args***);**

## DESCRIPTION

The **err**() and **warn**() family of functions display a formatted error message on the standard error output. In all cases, the last component of the program name, a colon character, and a space are output. If the *fmt* argument is not NULL, the [**printf**(3)](/printf/3.md)-like formatted error message is output. The output is terminated by a newline character.

The **err**(), **verr**(), **warn**(), and **vwarn**() functions append an error message obtained from [**strerror**(3)](/strerror/3.md) based on the global variable *errno*, preceded by another colon and space unless the *fmt* argument is NULL.

The **errx**() and **warnx**() functions do not append an error message.

The **err**(), **verr**(), **errx**(), and **verrx**() functions do not return, but exit with the value of the argument *eval*.

## ATTRIBUTES

For an explanation of the terms used in this section, see [**attributes**(7)](/attributes/7.md).

| | | |
| --- | --- | --- |
| **Interface** | **Attribute** | **Value** |
| **err**(), **errx**(), **warn**(), **warnx**(), **verr**(), **verrx**(), **vwarn**(), **vwarnx**() | Thread safety | MT-Safe locale |

## STANDARDS

BSD.

## HISTORY

- **err**() **warn**()

  4\.4BSD.

## EXAMPLES

Display the current *errno* information string and exit:

```
p = malloc(size);
if (p == NULL)
    err(EXIT_FAILURE, NULL);
fd = open(file_name, O_RDONLY, 0);
if (fd == -1)
    err(EXIT_FAILURE, "%s", file_name);
```

Display an error message and exit:

```
if (tm.tm_hour < START_TIME)
    errx(EXIT_FAILURE, "too early, wait until %s",
            start_time_string);
```

Warn of an error:

```
fd = open(raw_device, O_RDONLY, 0);
if (fd == -1)
    warnx("%s: %s: trying the block device",
            raw_device, strerror(errno));
fd = open(block_device, O_RDONLY, 0);
if (fd == -1)
    err(EXIT_FAILURE, "%s", block_device);
```

## SEE ALSO

[**error**(3)](/error/3.md), [**exit**(3)](/exit/3.md), [**perror**(3)](/perror/3.md), [**printf**(3)](/printf/3.md), [**strerror**(3)](/strerror/3.md)