strcmp()
Compare two strings
Synopsis:
#include <string.h>
int strcmp( const char* s1,
const char* s2 );
Arguments:
- s1, s2
- The strings that you want to compare.
Library:
libc
Use the -l c option to qcc to link against this library. This library is usually included automatically.
Description:
The strcmp() function compares the string pointed to by s1 to the string pointed to by s2.
Returns:
- < 0
- s1 is less than s2.
- 0
- s1 is equal to s2.
- > 0
- s1 is greater than s2.
Examples:
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
int main( void )
{
printf( "%d\n", strcmp( "abcdef", "abcdef" ) );
printf( "%d\n", strcmp( "abcdef", "abc" ) );
printf( "%d\n", strcmp( "abc", "abcdef" ) );
printf( "%d\n", strcmp( "abcdef", "mnopqr" ) );
printf( "%d\n", strcmp( "mnopqr", "abcdef" ) );
return EXIT_SUCCESS;
}
produces the output:
0
1
-1
-1
1
Environment variables:
- LIBC_STRINGS
- On certain targets, you can use this environment variable to select the implementation of
strcmp().
The value is one of the strings given below.
- for AArch64 targets:
- generic — the default
- for ARMv7 targets:
- 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.
- for AArch64 targets:
Classification:
| Safety: | |
|---|---|
| Cancellation point | No |
| Interrupt handler | Read the Caveats |
| Signal handler | Yes |
| Thread | Yes |
Caveats:
Implementations of strcmp() that are optimized using SIMD instructions aren't safe to use in an interrupt handler. These include the NEON implementations on ARMv7 and AArch64.
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