strchr()

Find the first occurrence of a character in a string

Synopsis:

#include <string.h>

char* strchr(char* s, 
              int c );

Arguments:

s
The string that you want to search.
c
The character that you're looking for.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The strchr() function finds the first occurrence of c (converted to a char) in the string pointed to by s. The terminating NUL character is considered to be part of the string.

Returns:

A pointer to the located character, or NULL if c doesn't occur in the string.

Examples:

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

int main( void )
{
    char buffer[80];
    char* where;

    strcpy( buffer, "video x-rays" );

    where = strchr( buffer, 'x' );

    if( where == NULL ) {
        printf( "'x' not found\n" );
    } else {
        printf( "'x' found: %s\n", where );
    }

    return EXIT_SUCCESS;
}

Environment variables:

LIBC_STRINGS
On 32-bit ARMv7 targets, you can use this environment variable to select the implementation for this function. The value is one of the following:
  • cortex_a9 — optimized for the ARM Cortex-A9 processor; assumes that no unaligned access is supported.
  • cortex_a9_aligned — optimized for ARM Cortex-A9; requires that unaligned memory access be enabled on the platform. If memory access is misaligned, this implementation falls back to the NEON version.
  • cortex_a9_neon — optimized for ARM Cortex-A9 using NEON.
  • generic — the default.
  • krait — optimized for the Qualcomm Krait CPU.
  • krait_neon — optimized for Qualcomm Krait using NEON.

Processes that register ISRs shouldn't use the NEON versions.

LD_PRELOAD
To use the implementation for this function that's optimized for ARM 64-bit architecture, you must set this environment variable. For example:
# export LD_PRELOAD=/lib/libstringsa64.so
            

Classification:

ANSI, POSIX 1003.1

Safety:  
Cancellation point No
Interrupt handler Read the Caveats
Signal handler Yes
Thread Yes

Caveats:

If you're using the implementation for this function that's optimized for ARM 64-bit architecture, it's unsafe to use it in an interrupt handler.