tools: iio: Send error messages to stderr

---
 tools/iio/generic_buffer.c    | 39 ++++++++++++++++++---------------
 tools/iio/iio_event_monitor.c | 14 ++++++------
 tools/iio/iio_utils.c         | 51 +++++++++++++++++++++++++------------------
 tools/iio/lsiio.c             |  2 +-
 4 files changed, 59 insertions(+), 47 deletions(-)
 
diff --git a/tools/iio/generic_buffer.c b/tools/iio/generic_buffer.c
index 9535c2d..32f389eb 100644
--- a/tools/iio/generic_buffer.c
+++ b/tools/iio/generic_buffer.c
@@ -193,15 +193,15 @@ void process_scan(char *data,
 
 void print_usage(void)
 {
-	printf("Usage: generic_buffer [options]...\n"
-	       "Capture, convert and output data from IIO device buffer\n"
-	       "  -c <n>     Do n conversions\n"
-	       "  -e         Disable wait for event (new data)\n"
-	       "  -g         Use trigger-less mode\n"
-	       "  -l <n>     Set buffer length to n samples\n"
-	       "  -n <name>  Set device name (mandatory)\n"
-	       "  -t <name>  Set trigger name\n"
-	       "  -w <n>     Set delay between reads in us (event-less mode)\n");
+	fprintf(stderr, "Usage: generic_buffer [options]...\n"
+		"Capture, convert and output data from IIO device buffer\n"
+		"  -c <n>     Do n conversions\n"
+		"  -e         Disable wait for event (new data)\n"
+		"  -g         Use trigger-less mode\n"
+		"  -l <n>     Set buffer length to n samples\n"
+		"  -n <name>  Set device name (mandatory)\n"
+		"  -t <name>  Set trigger name\n"
+		"  -w <n>     Set delay between reads in us (event-less mode)\n");
 }
 
 int main(int argc, char **argv)
@@ -271,7 +271,7 @@ int main(int argc, char **argv)
 	}
 
 	if (!device_name) {
-		printf("Device name not set\n");
+		fprintf(stderr, "Device name not set\n");
 		print_usage();
 		return -1;
 	}
@@ -279,7 +279,7 @@ int main(int argc, char **argv)
 	/* Find the device requested */
 	dev_num = find_type_by_name(device_name, "iio:device");
 	if (dev_num < 0) {
-		printf("Failed to find the %s\n", device_name);
+		fprintf(stderr, "Failed to find the %s\n", device_name);
 		return dev_num;
 	}
 
@@ -307,7 +307,8 @@ int main(int argc, char **argv)
 		/* Verify the trigger exists */
 		trig_num = find_type_by_name(trigger_name, "trigger");
 		if (trig_num < 0) {
-			printf("Failed to find the trigger %s\n", trigger_name);
+			fprintf(stderr, "Failed to find the trigger %s\n",
+				trigger_name);
 			ret = trig_num;
 			goto error_free_triggername;
 		}
@@ -323,8 +324,8 @@ int main(int argc, char **argv)
 	 */
 	ret = build_channel_array(dev_dir_name, &channels, &num_channels);
 	if (ret) {
-		printf("Problem reading scan element information\n");
-		printf("diag %s\n", dev_dir_name);
+		fprintf(stderr, "Problem reading scan element information\n"
+			"diag %s\n", dev_dir_name);
 		goto error_free_triggername;
 	}
 
@@ -350,7 +351,8 @@ int main(int argc, char **argv)
 						    dev_dir_name,
 						    trigger_name);
 		if (ret < 0) {
-			printf("Failed to write current_trigger file\n");
+			fprintf(stderr,
+				"Failed to write current_trigger file\n");
 			goto error_free_buf_dir_name;
 		}
 	}
@@ -382,7 +384,7 @@ int main(int argc, char **argv)
 	fp = open(buffer_access, O_RDONLY | O_NONBLOCK);
 	if (fp == -1) { /* TODO: If it isn't there make the node */
 		ret = -errno;
-		printf("Failed to open %s\n", buffer_access);
+		fprintf(stderr, "Failed to open %s\n", buffer_access);
 		goto error_free_buffer_access;
 	}
 
@@ -410,7 +412,7 @@ int main(int argc, char **argv)
 		read_size = read(fp, data, toread * scan_size);
 		if (read_size < 0) {
 			if (errno == EAGAIN) {
-				printf("nothing available\n");
+				fprintf(stderr, "nothing available\n");
 				continue;
 			} else {
 				break;
@@ -431,7 +433,8 @@ int main(int argc, char **argv)
 		ret = write_sysfs_string("trigger/current_trigger",
 					 dev_dir_name, "NULL");
 		if (ret < 0)
-			printf("Failed to write to %s\n", dev_dir_name);
+			fprintf(stderr, "Failed to write to %s\n",
+				dev_dir_name);
 
 error_close_buffer_access:
 	if (close(fp) == -1)
diff --git a/tools/iio/iio_event_monitor.c b/tools/iio/iio_event_monitor.c
index 9ee1959..cd3fd41 100644
--- a/tools/iio/iio_event_monitor.c
+++ b/tools/iio/iio_event_monitor.c
@@ -215,8 +215,8 @@ static void print_event(struct iio_event_data *event)
 	bool diff = IIO_EVENT_CODE_EXTRACT_DIFF(event->id);
 
 	if (!event_is_known(event)) {
-		printf("Unknown event: time: %lld, id: %llx\n",
-		       event->timestamp, event->id);
+		fprintf(stderr, "Unknown event: time: %lld, id: %llx\n",
+			event->timestamp, event->id);
 
 		return;
 	}
@@ -251,7 +251,7 @@ int main(int argc, char **argv)
 	int fd, event_fd;
 
 	if (argc <= 1) {
-		printf("Usage: %s <device_name>\n", argv[0]);
+		fprintf(stderr, "Usage: %s <device_name>\n", argv[0]);
 		return -1;
 	}
 
@@ -277,14 +277,14 @@ int main(int argc, char **argv)
 	fd = open(chrdev_name, 0);
 	if (fd == -1) {
 		ret = -errno;
-		fprintf(stdout, "Failed to open %s\n", chrdev_name);
+		fprintf(stderr, "Failed to open %s\n", chrdev_name);
 		goto error_free_chrdev_name;
 	}
 
 	ret = ioctl(fd, IIO_GET_EVENT_FD_IOCTL, &event_fd);
 	if (ret == -1 || event_fd == -1) {
 		ret = -errno;
-		fprintf(stdout, "Failed to retrieve event fd\n");
+		fprintf(stderr, "Failed to retrieve event fd\n");
 		if (close(fd) == -1)
 			perror("Failed to close character device file");
 
@@ -300,7 +300,7 @@ int main(int argc, char **argv)
 		ret = read(event_fd, &event, sizeof(event));
 		if (ret == -1) {
 			if (errno == EAGAIN) {
-				printf("nothing available\n");
+				fprintf(stderr, "nothing available\n");
 				continue;
 			} else {
 				ret = -errno;
@@ -310,7 +310,7 @@ int main(int argc, char **argv)
 		}
 
 		if (ret != sizeof(event)) {
-			printf("Reading event failed!\n");
+			fprintf(stderr, "Reading event failed!\n");
 			ret = -EIO;
 			break;
 		}
diff --git a/tools/iio/iio_utils.c b/tools/iio/iio_utils.c
index e177f40..c3f9e37 100644
--- a/tools/iio/iio_utils.c
+++ b/tools/iio/iio_utils.c
@@ -140,7 +140,8 @@ int iioutils_get_type(unsigned *is_signed, unsigned *bytes, unsigned *bits_used,
 			sysfsfp = fopen(filename, "r");
 			if (!sysfsfp) {
 				ret = -errno;
-				printf("failed to open %s\n", filename);
+				fprintf(stderr, "failed to open %s\n",
+					filename);
 				goto error_free_filename;
 			}
 
@@ -152,11 +153,13 @@ int iioutils_get_type(unsigned *is_signed, unsigned *bytes, unsigned *bits_used,
 				     &padint, shift);
 			if (ret < 0) {
 				ret = -errno;
-				printf("failed to pass scan type description\n");
+				fprintf(stderr,
+					"failed to pass scan type description\n");
 				goto error_close_sysfsfp;
 			} else if (ret != 5) {
 				ret = -EIO;
-				printf("scan type description didn't match\n");
+				fprintf(stderr,
+					"scan type description didn't match\n");
 				goto error_close_sysfsfp;
 			}
 
@@ -170,7 +173,8 @@ int iioutils_get_type(unsigned *is_signed, unsigned *bytes, unsigned *bits_used,
 			*is_signed = (signchar == 's');
 			if (fclose(sysfsfp)) {
 				ret = -errno;
-				printf("Failed to close %s\n", filename);
+				fprintf(stderr, "Failed to close %s\n",
+					filename);
 				goto error_free_filename;
 			}
 
@@ -454,7 +458,8 @@ int build_channel_array(const char *device_dir,
 			sysfsfp = fopen(filename, "r");
 			if (!sysfsfp) {
 				ret = -errno;
-				printf("failed to open %s\n", filename);
+				fprintf(stderr, "failed to open %s\n",
+					filename);
 				free(filename);
 				goto error_cleanup_array;
 			}
@@ -568,7 +573,7 @@ int find_type_by_name(const char *name, const char *type)
 
 	dp = opendir(iio_dir);
 	if (!dp) {
-		printf("No industrialio devices available\n");
+		fprintf(stderr, "No industrialio devices available\n");
 		return -ENODEV;
 	}
 
@@ -581,11 +586,13 @@ int find_type_by_name(const char *name, const char *type)
 			ret = sscanf(ent->d_name + strlen(type), "%d", &number);
 			if (ret < 0) {
 				ret = -errno;
-				printf("failed to read element number\n");
+				fprintf(stderr,
+					"failed to read element number\n");
 				goto error_close_dir;
 			} else if (ret != 1) {
 				ret = -EIO;
-				printf("failed to match element number\n");
+				fprintf(stderr,
+					"failed to match element number\n");
 				goto error_close_dir;
 			}
 
@@ -664,7 +671,7 @@ static int _write_sysfs_int(const char *filename, const char *basedir, int val,
 	sysfsfp = fopen(temp, "w");
 	if (!sysfsfp) {
 		ret = -errno;
-		printf("failed to open %s\n", temp);
+		fprintf(stderr, "failed to open %s\n", temp);
 		goto error_free;
 	}
 
@@ -685,7 +692,7 @@ static int _write_sysfs_int(const char *filename, const char *basedir, int val,
 		sysfsfp = fopen(temp, "r");
 		if (!sysfsfp) {
 			ret = -errno;
-			printf("failed to open %s\n", temp);
+			fprintf(stderr, "failed to open %s\n", temp);
 			goto error_free;
 		}
 
@@ -703,8 +710,9 @@ static int _write_sysfs_int(const char *filename, const char *basedir, int val,
 		}
 
 		if (test != val) {
-			printf("Possible failure in int write %d to %s/%s\n",
-			       val, basedir, filename);
+			fprintf(stderr,
+				"Possible failure in int write %d to %s/%s\n",
+				val, basedir, filename);
 			ret = -1;
 		}
 	}
@@ -750,7 +758,7 @@ static int _write_sysfs_string(const char *filename, const char *basedir,
 	char *temp = malloc(strlen(basedir) + strlen(filename) + 2);
 
 	if (!temp) {
-		printf("Memory allocation failed\n");
+		fprintf(stderr, "Memory allocation failed\n");
 		return -ENOMEM;
 	}
 
@@ -761,7 +769,7 @@ static int _write_sysfs_string(const char *filename, const char *basedir,
 	sysfsfp = fopen(temp, "w");
 	if (!sysfsfp) {
 		ret = -errno;
-		printf("Could not open %s\n", temp);
+		fprintf(stderr, "Could not open %s\n", temp);
 		goto error_free;
 	}
 
@@ -782,7 +790,7 @@ static int _write_sysfs_string(const char *filename, const char *basedir,
 		sysfsfp = fopen(temp, "r");
 		if (!sysfsfp) {
 			ret = -errno;
-			printf("Could not open file to verify\n");
+			fprintf(stderr, "Could not open file to verify\n");
 			goto error_free;
 		}
 
@@ -800,9 +808,10 @@ static int _write_sysfs_string(const char *filename, const char *basedir,
 		}
 
 		if (strcmp(temp, val) != 0) {
-			printf("Possible failure in string write of %s "
-			       "Should be %s written to %s/%s\n", temp, val,
-			       basedir, filename);
+			fprintf(stderr,
+				"Possible failure in string write of %s "
+				"Should be %s written to %s/%s\n", temp, val,
+				basedir, filename);
 			ret = -1;
 		}
 	}
@@ -856,7 +865,7 @@ int read_sysfs_posint(const char *filename, const char *basedir)
 	char *temp = malloc(strlen(basedir) + strlen(filename) + 2);
 
 	if (!temp) {
-		printf("Memory allocation failed");
+		fprintf(stderr, "Memory allocation failed");
 		return -ENOMEM;
 	}
 
@@ -903,7 +912,7 @@ int read_sysfs_float(const char *filename, const char *basedir, float *val)
 	char *temp = malloc(strlen(basedir) + strlen(filename) + 2);
 
 	if (!temp) {
-		printf("Memory allocation failed");
+		fprintf(stderr, "Memory allocation failed");
 		return -ENOMEM;
 	}
 
@@ -950,7 +959,7 @@ int read_sysfs_string(const char *filename, const char *basedir, char *str)
 	char *temp = malloc(strlen(basedir) + strlen(filename) + 2);
 
 	if (!temp) {
-		printf("Memory allocation failed");
+		fprintf(stderr, "Memory allocation failed");
 		return -ENOMEM;
 	}
 
diff --git a/tools/iio/lsiio.c b/tools/iio/lsiio.c
index 4f8172f..b271a9a 100644
--- a/tools/iio/lsiio.c
+++ b/tools/iio/lsiio.c
@@ -108,7 +108,7 @@ static int dump_devices(void)
 
 	dp = opendir(iio_dir);
 	if (!dp) {
-		printf("No industrial I/O devices available\n");
+		fprintf(stderr, "No industrial I/O devices available\n");
 		return -ENODEV;
 	}