---
name: "SetErrno"
section: "3"
platform: "macos"
package: "tcl"
version: "152"
release: "macOS 26.5"
platforms: ["macos"]
url: "https://new.carta.tech/SetErrno"
---

# SetErrno(3)

manipulate errno to store and retrieve error codes

## NAME

Tcl\_SetErrno, Tcl\_GetErrno, Tcl\_ErrnoId, Tcl\_ErrnoMsg - manipulate errno to store and retrieve error codes

## SYNOPSIS

```
#include <tcl.h>

void
Tcl_SetErrno(errorCode)

int
Tcl_GetErrno()

const char *
Tcl_ErrnoId()

const char *
Tcl_ErrnoMsg(errorCode)

```

## ARGUMENTS

A POSIX error code such as **ENOENT**.

## DESCRIPTION

**Tcl\_SetErrno** and **Tcl\_GetErrno** provide portable access to the **errno** variable, which is used to record a POSIX error code after system calls and other operations such as **Tcl\_Gets**. These procedures are necessary because global variable accesses cannot be made across module boundaries on some platforms.

**Tcl\_SetErrno** sets the **errno** variable to the value of the *errorCode* argument C procedures that wish to return error information to their callers via **errno** should call **Tcl\_SetErrno** rather than setting **errno** directly.

**Tcl\_GetErrno** returns the current value of **errno**. Procedures wishing to access **errno** should call this procedure instead of accessing **errno** directly.

**Tcl\_ErrnoId** and **Tcl\_ErrnoMsg** return string representations of **errno** values.  **Tcl\_ErrnoId** returns a machine-readable textual identifier such as that corresponds to the current value of **errno**. **Tcl\_ErrnoMsg** returns a human-readable string such as that corresponds to the value of its *errorCode* argument.  The *errorCode* argument is typically the value returned by **Tcl\_GetErrno**. The strings returned by these functions are statically allocated and the caller must not free or modify them.

## KEYWORDS

errno, error code, global variables