Compilare: user.c: In function ‘main’: user.c:33:21: warning: implicit declaration of function ‘strlen’ [-Wimplicit-function-declaration] for (i = 0; i < strlen(v); i++) ^~~~~~ user.c:33:21: warning: incompatible implicit declaration of built-in function ‘strlen’ user.c:33:21: note: include ‘<string.h>’ or provide a declaration of ‘strlen’ user.c:39:13: warning: this ‘else’ clause does not guard... [-Wmisleading-indentation] else ^~~~ user.c:41:17: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the ‘else’ i++; ^ user.c:58:25: warning: incompatible implicit declaration of built-in function ‘strlen’ for (i = 2; i < strlen(v); i++) ^~~~~~ user.c:58:25: note: include ‘<string.h>’ or provide a declaration of ‘strlen’ user.c:26:5: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(f, "%d", &p); ^~~~~~~~~~~~~~~~~~~ user.c:27:5: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(f, "%s", v); ^~~~~~~~~~~~~~~~~~