Advanced Programming in the UNIX® Environment

ptg10805159

380 Signals Chapter 10

It operates in a similar manner to thepsignalfunction. Although this function has

access to moreinformation than just the signal number,platforms vary in exactly what

additional information is printed.

If you only need the string description of the signal and don’t necessarily want to

write it to standarderror (you might want to write it to a log file, for example), you can

use thestrsignalfunction. This function is similar tostrerror(also described in

Section 1.7).

#include <string.h>

char *strsignal(intsigno);

Returns: a pointer to a string describing the signal

Given a signal number,strsignalwill return a string that describes the signal. This

string can be used by applications to print error messages about signals received.

All the platforms discussed in this book provide thepsignalandstrsignalfunctions, but

differences do occur.OnSolaris 10,strsignalwill return a null pointer if the signal number

is invalid, whereas FreeBSD 8.0, Linux 3.2.0, and Mac OS X 10.6.8 return a string indicating

that the signal number is unrecognized.

Only Linux 3.2.0 and Solaris 10 support thepsiginfofunction.

Solaris provides a couple of functions to map a signal number to a signal name, and

vice versa.

#include <signal.h>

int sig2str(intsigno,char *str);

int str2sig(const char *str,int *signop);

Both return: 0 if OK,−1 on error

These functions areuseful when writing interactive programs that need to accept and

print signal names and numbers.

Thesig2strfunction translates the given signal number into a string and stores

the result in the memory pointed to bystr.The caller must ensurethat the memory is

large enough to hold the longest string, including the terminating null byte. Solaris

provides the constantSIG2STR_MAXin<signal.h>to define the maximum string

length. The string consists of the signal name without the ‘‘SIG’’prefix. For example,

translatingSIGKILLwould result in the string ‘‘KILL’’ being stored in thestrmemory

buffer.

Thestr2sigfunction translates the given name into a signal number.The signal

number is stored in the integer pointed to bysignop.The name can be either the signal

name without the ‘‘SIG’’prefix or a string representation of the decimal signal number

(i.e., ‘‘9’’).

Note thatsig2strandstr2sigdepart from common practice and don’t set

errnowhen they fail.