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@nshalman
Last active August 29, 2015 14:01
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grep that preserves the header line
/*
* This is free and unencumbered software released into the public domain.
*
* Anyone is free to copy, modify, publish, use, compile, sell, or
* distribute this software, either in source code form or as a compiled
* binary, for any purpose, commercial or non-commercial, and by any
* means.
*
* In jurisdictions that recognize copyright laws, the author or authors
* of this software dedicate any and all copyright interest in the
* software to the public domain. We make this dedication for the benefit
* of the public at large and to the detriment of our heirs and
* successors. We intend this dedication to be an overt act of
* relinquishment in perpetuity of all present and future rights to this
* software under copyright law.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
* IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
* OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*
* For more information, please refer to <http://unlicense.org/>
*/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#define MAX_DATA 4096
int main(int argc, char* argv[])
{
// Unset FD_CLOEXEC
fcntl(STDIN_FILENO, F_SETFD, fcntl(STDIN_FILENO, F_GETFD) & (~FD_CLOEXEC));
fcntl(STDOUT_FILENO, F_SETFD, fcntl(STDOUT_FILENO, F_GETFD) & (~FD_CLOEXEC));
fcntl(STDERR_FILENO, F_SETFD, fcntl(STDERR_FILENO, F_GETFD) & (~FD_CLOEXEC));
// Disable buffering, print first line, enable line buffering
setvbuf(stdin, NULL, _IONBF, 0);
char buffer[MAX_DATA];
if (fgets(buffer, MAX_DATA, stdin)) {
fputs(buffer, stdout);
}
else {
exit(1);
}
setlinebuf(stdin);
// Flush stdout, exec grep
fflush(stdout);
return execvp("grep", argv);
}
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