[PATCH 3/7] test: In pasta demo, use pgrep instead of pstree to find namespace PID

[Stefano Brivio <sbrivio@redhat.com>]

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Parsing pstree's output is somewhat unreliable: there might be
multiple pasta instances running on the same host, and depending on
the overall output width pstree might truncate some branches.

Ask pasta to save its PID to file, and use that as parameter for
pgrep to find the PID of the interactive shell whose user and network
namespaces we want to join.

Signed-off-by: Stefano Brivio <sbrivio(a)redhat.com>
---
 test/demo/pasta | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/test/demo/pasta b/test/demo/pasta
index f4b7da2..be117b3 100644
--- a/test/demo/pasta
+++ b/test/demo/pasta
@@ -48,7 +48,7 @@ nl
 say	  without PID, it will create a namespace.
 sleep	3
 passt	cd __TEMPDIR__/passt
-passtb	./pasta
+passtb	./pasta -P /tmp/pasta.pid
 sleep	3
 
 nl
@@ -57,8 +57,7 @@ say	For convenience, let's enter this namespace
 nl
 say	  from another terminal.
 sleep	3
-ns	pstree -p | grep pasta
-nsout	TARGET_PID pstree -p | grep pasta | sed -n 's/.*(\([0-9].*\))$/\1/p'
+nsout	TARGET_PID pgrep -P $(cat /tmp/pasta.pid)
 sleep	1
 
 ns	nsenter -t __TARGET_PID__ -U -n --preserve-credentials
@@ -171,10 +170,10 @@ passt	exit
 passt	make clean
 passt	CFLAGS="-g" make
 sleep	2
-passtb	perf record -g ./pasta
+passtb	perf record -g ./pasta -P /tmp/pasta.pid
 sleep	2
 
-nsout	TARGET_PID pstree -p | grep pasta | sed -n 's/.*(\([0-9].*\))$/\1/p'
+nsout	TARGET_PID pgrep -P $(cat /tmp/pasta.pid)
 sleep	1
 ns	nsenter -t __TARGET_PID__ -U -n --preserve-credentials
 sleep	5
-- 
@@ -48,7 +48,7 @@ nl
 say	  without PID, it will create a namespace.
 sleep	3
 passt	cd __TEMPDIR__/passt
-passtb	./pasta
+passtb	./pasta -P /tmp/pasta.pid
 sleep	3
 
 nl
@@ -57,8 +57,7 @@ say	For convenience, let's enter this namespace
 nl
 say	  from another terminal.
 sleep	3
-ns	pstree -p | grep pasta
-nsout	TARGET_PID pstree -p | grep pasta | sed -n 's/.*(\([0-9].*\))$/\1/p'
+nsout	TARGET_PID pgrep -P $(cat /tmp/pasta.pid)
 sleep	1
 
 ns	nsenter -t __TARGET_PID__ -U -n --preserve-credentials
@@ -171,10 +170,10 @@ passt	exit
 passt	make clean
 passt	CFLAGS="-g" make
 sleep	2
-passtb	perf record -g ./pasta
+passtb	perf record -g ./pasta -P /tmp/pasta.pid
 sleep	2
 
-nsout	TARGET_PID pstree -p | grep pasta | sed -n 's/.*(\([0-9].*\))$/\1/p'
+nsout	TARGET_PID pgrep -P $(cat /tmp/pasta.pid)
 sleep	1
 ns	nsenter -t __TARGET_PID__ -U -n --preserve-credentials
 sleep	5
-- 
2.35.1